OFFICIAL EXPLANATION



THE PROMPT

• Issues?
→ Subject/verb agreement
The subject three of the most encouraging ideas is plural.

→ list item parallelism
The ideas are listed. Because the ideas are part of a list, the items must be parallel: they must be of the same grammatical form and play similar logical roles.

THE OPTIONS

• the singular verb includes does not agree with the plural subject

• restoring, refueling, and to detach are not parallel.
→ to detach is an infinitive. The other two words are gerunds (noun verbING words). Not parallel.
ELIMINATE A


• I do not see any errors
→ the plural verb include agrees with the plural subject
→ restoring, refueling, and detaching
→ only one pronoun, them, exists, and it refers to working parts.

If you have doubts about the pronoun them in option B,
(1) remember that the other four options contain clear grammatical errors and are worse than B, and
(2) see my post below by clicking here.
In that post, I addressed the issue surrounding the pronoun them.


• not parallel
to restore, refueling, and by detaching
infinitive, gerund (verbING noun), and [preposition + gerund]
Those three are not similar parts of speech expressed similarly.
ELIMINATE C


• the verb includes is singular and does not agree with the plural subject
ELIMINATE D


• them cannot be used for both satellites and working parts
→ GMAC allows two different plural pronouns that refer to two different nouns (they and their in on official question refer to two different nouns), but
→ once "them" refers to satellites in the second list item, the pronoun "them" can refer only to satellites
→ in the third item on the list, them seems to refer to working parts
I do not think we have a case of pronoun ambiguity.
I am not remotely tempted to view the second "them" as referring to "satellites."
Logically, such reference does not make sense.
We do have a case of pronoun misuse: "them" belongs to satellites and cannot refer to a different noun such as working parts.

• from old ones is badly misplaced
→ from old ones = from old satellites
→ this phrase modifies working parts and should not be placed so far from its noun.
ELIMINATE E

The best answer is B

COMMENTS

Although some of these answers contain somewhat abrupt explanation, in terms of analysis, they're all good.

I'm glad to see that people are working hard.
Maintaining discipline under normal circumstances is difficult; maintaining discipline under abnormal circumstances can be herculean at times.
Be proud of yourselves.
You all have done good work.

Parallel structure: restoring, refueling and detaching
Subject verb: Three ideas...include

A) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones. ok

C) are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones.

D) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones.

IMO B

My choice is (B). It took me 1:11.

First, the subject is plural ("Three of the most encouraging ideas"). Eliminate A and D.

Second, for a list of three items ("X, Y, and Z"), it is imperative to have parallelism between X, Y, and Z.
In (B), "restoring ...", "refueling ..." and "detaching ..." are parallel.
In (C), "to restore", "refueling" and "by detaching" are not parallel. Eliminate C.
In (E), "restoring ...", "using..." and "detaching" also seems to be parallel.

Finally, compare (B) and (E).
For (B), at first, I do not like the them in attach them: detaching working parts from old satellites to attach them to new ones.
It does not feel right.
Better: detaching working parts from old satellites to be reused in new ones.
I wonder if others feel the same.
It turns out (E) uses the similar construct: detaching working parts to attach them to new satellites from old ones
It is actually worse.

But I eliminate (E) based on "using a traveling service station that refuels them". It introduces a subordinate clause.
In this list, the first item is "restoring power via a mission extension vehicle". There is no use of subordinate clause.
In (B), "refueling via a type of traveling service station" is more consistent with "restoring power via a mission extension vehicle".

Three of the most encouraging ideas to extend the life of satellites includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

1. Subject - Three of the most encouraging ideas - Plural => drop A & D straight off.

2. Look for perfect //m between three ideas. - C and E introduces //m error drop them as well

Pick B, and move.

A) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.

C) are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones.

D) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones.

IMO B
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IMO B

We are talking about Ideas Plural -- includes refers to singular nouns and hence eliminate A & D

C is not parellel
- are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones. -- Marked the unparellel words in bold - its a complete mess.


B Vs E

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones. - ok

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones. - meaning Error and unnecessarily long sentence.. Also what does THEM refer to ?!

zhanbo, I totally agree with you, The third idea, "detaching working parts to attach them to new satellites from old ones."

I think we can eliminate them can it should be fine.

let's see what generis has to say about it.
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IMO B.

Three of the most encouraging ideas to extend the life of satellites includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

This question checks Subject verb agreement and Parallelism understanding.

A) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.-> We have subject "Three of the most encouraging ideas" plural, so includes (singular) is incorrect.

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.-> Subject verb agreement is improved. Now, List items, restoring power..., refueling.... and detaching....are parallel too. Let's keep it.

C) are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones.-> List items, to restore power..., refueling.... and by detaching....are not parallel.

D) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.-> We have subject "Three of the most encouraging ideas" plural, so includes (singular) is incorrect.

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones.-> using is incorrect to use. We need refueling.

So, I think B.

Three of the most encouraging ideas to extend the life of satellites includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

A) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.
Subject verb error "ideas .. includes". Out.

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.
Looks fine. || and meaning retained.

C) are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones.
to restore power is not || with refueling ... and by detaching.. Out.

D) includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.
Same reasoning as A.

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones.
Meaning changed in 'using a traveling service station ..'. Also, what is 'them referring' too? Out.

IMO B

Three of the most encouraging ideas to extend the life of satellites includes restoring power via a mission extension vehicle, refueling via a type of traveling service station, and to detach working parts from old satellites to attach them to new ones.

Straight off ideas -> include (not includes)
2:3 split
Eliminate A and D

B) include restoring power via a mission extension vehicle, refueling via a type of traveling service station, and detaching working parts from old satellites to attach them to new ones.
Parallelism/idiom/ grammar -perfect and correct.

C) are to restore power via a mission extension vehicle, refueling via a type of traveling service station, and by detaching working parts from old satellites to attach them to new ones.
Faulty parallelism.
From X to Y <verb is not required>

E) include restoring power via a mission extension vehicle, using a traveling service station that refuels them, and detaching working parts to attach them to new satellites from old ones.
wordy

zhanbo wrote:


callmeDP wrote:

Well, what generis has to say about these issues was Swype-typed hours ago on a phone in a parking lot into which I pulled my car after I glanced at my phone at a stoplight. That scrolling-on-a-phone business is for the birds. (Vernacular. Google it.)

• THE PRONOUN THEM
Is the pronoun usage logical? Watch the action words, adjectives, and prepositional phrases that are connected to the pronouns.
Option B: . . .
→ detaching working parts
→ from old satellites
→ [in order] to attach them
→ to new ones

Stylistic parallelism may help you to see logical connections between the nouns and pronouns at issue.

What gets detached? And from what?
What gets attached? And to what?

The sentence concerns methods by which to extend the life of a machine.
The words “detached” and “attached” are logically connected.

It is logical to assume that whatever got detached in this preemptive fix also gets attached, especially because the small parts were “detached” from certain large OLD things and subsequently “attached” to – what? To “NEW ones.”

(In other words, if new satellites break, people should use working parts from old satellites to repair the new satellites. Repurposed parts save time and money that would be spent making them. From that fact we could easily construct an argument that the repurposed parts “extend the life” of satellites.)

After we examine function words (detaching and [in order] to attach), adjectives (old and new), and prepositional adjective phrases (which begin with from and to), we should notice that the two different plural pronouns (them and ones) are logically distinguished by the words that surround or are attached to those pronouns.
→ The word them is connected to attachment and thus logically also to the parallel action of detachment.
We know exactly what is detached. Those same things are the logical candidates for what is subsequently attached elsewhere.
→ The word ones is qualified by a size word, the adjective new. That adjective, in turn, is parallel to old.
We know exactly what is old.

The satellites were not detached from themselves. That sentence is nonsensical.
To what, then, must the word them refer?

Regarding option E, let’s take a look at the last phrase:
. . . and detaching working parts to attach them to new satellites from old ones.

Examine the placement of the modifier from old ones.
First, with respect to pronoun ambiguity (which is actually pretty rare on the GMAT), decide what you think ones refers to.
Then decide what this prepositional adjective phrase should modify (after having replaced ones with the most likely noun candidate.

→ When in doubt, replace the pronoun with what you think is the correct noun.
Does the replacement make sense? If so, the pronoun usage is probably logical.
→ Now replace the pronoun with the other noun. The replacement should not make sense.

• USING = ACTION NOUN a.k.a. gerund a.k.a verbING

Subordinate clause vs. gerund (verbING)?

I am utterly lost with respect to the claim that the phrase “using XYZ” introduces a subordinate clause into a list.

Since when did the noun “using” automatically create a subordinate clause? And why does the word do so?
Is some weird rule being taught that I have never seen? Is this rule floating around and merrily mucking up approaches to SC?

Consider this sentence:
Good hand hygiene consists of washing with soap and warm water, using 70 percent ethanol-based sanitizer when a sink is not available, and wearing disposable gloves when disinfecting surfaces that have been contaminated by pathogens.
→ washing, using, wearing

Food for thought.

I hope that analysis helps.
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The official explanation is here.