According to a report released by Oxfam the most successful nations

OFFICIAL EXPLANATION


THE PROMPT
Issues?
• subject/verb agreement
→ the subject is nations (plural, obviously)
"of the world" is a modifier that tells us more about "nations"
"OF the world" is a prepositional modifier designed to trick you into focusing on the singular word world
In GMAT grammar-speak, nations is the "head" or "anchor" noun in a noun phrase.

• verb tense
→ simple present (consumes and are) versus
-- present progressive/continuous (are consuming and are being)
-- present perfect (have [now] been)

• meaning when the sentence is read as a whole
Try to train yourself to leave a few seconds to insert your chosen answer into the whole sentence (read "out loud" in your head)
Two of these sentences are at best unidiomatic and at worse nonsensical.

• parallelism
Unless the parallelism errors are obvious or you are deadly at parallelism, try to eliminate answers on other bases.
On occasion, as is the case in this question, you can avoid having to cope with parallelism.
Assessing parallelism is usually harder than spotting subject/verb agreement error or verb tense error. Don't be a hero.

→ Not only [X] but also [Y]
X and Y must be parallel, i.e. must play the same logical role in the sentence and be similar parts of speech.

Take note: The way that the part of speech is constructed often does not have to be identical.
In a list of nouns, for example, some may be accompanied by adjectives while others may not.**

Parallelism can be a bit tricky with Not only X but also Y.
The most common method is to examine what comes right after each of the two parts of the coordinating conjunction, a method I use in analyzing the options.
(1) what follows "not only" does not automatically "carry over" to "but also"
(2) whatever follows both word pairs must be similar parts of speech and play the same logical role

THE OPTIONS - inserted into a shortened prompt
• consumes should be consume
→ the subject, nations, requires a plural verb

• not parallel
not only is followed by a verb, consumes
but also is "followed" by a clause, they are also now home to more than half of the world's poorest people.
→ I write "followed" because diction allows the they to be interspersed with but also.
Each part of the structure is followed by different grammatical structures (parts of speech). A verb and a clause are not parallel.

ELIMINATE A
• nations . . . consume is correct: subject and verb are both plural
• parallelism is maintained
→ not only [verb] . . . but also [verb]
KEEP B

• consumes should be consume
→ the subject, nations, requires a plural verb

• the verb tense are being (present progressive/continuous) is not correct for situations in which we are describing a general truth. Use simple present.

• the words are now being home make the sentence nonsensical (and at the least, unidiomatic)
→ are being home is not a thing in English.
are being must be followed by a past participle (a verbED) or an adjective.
Correct: We are being bamboozled by consumerist propaganda.
Correct: We are being careful to follow mask-wearing guidelines to the letter.

Don't memorize what I just wrote. If you read 15 minutes a day, "nations are now being home to poor people" will strike you as off. The phrasing sounds as if the nations themselves are somehow at home.
Finally,
→ remove the word being
If the meaning is not affected, being is not necessary.
If the meaning is improved, being is almost certainly wrong.
ELIMINATE C

• have now been (present perfect) is not the correct verb tense
→ again, to report facts, use simple present tense: are
→ present perfect bridges the past and present and describes an event that started at some vague time before now and that continues into the present.
If no time word exists (as is the case in this sentence), this verb tense is usually used to describe an unfinished event or to emphasize a result.
→ More than 100 Republicans have formally declared their support for a lawsuit that the Supreme Court is likely to throw out.
→ Scientists have developed a vaccine that is 95 percent effective.

• have now been makes very little sense
→ We can say that these nations have been home to half the world's poor people for two years or two decades, or that these nations have recently become home to half the world's poor, but in this sentence, "have now been" is nonsensical. The sentence needs a time frame.

• not parallel
→ not only is followed by a verb (consume)
→ but also is followed by a clause (they have now been[/color] home to .. .[/i])
ELIMINATE D

• are not only consuming should be not only consume
→ to discuss general truths or facts, we use simple present tense, consume.

The present progressive (are consuming) is used to talk about things that are happening right now and that are usually unfinished or incomplete.
→ This moment: You are reading a GMAT Club post.
→ During this time period (often a trend): More and more often, concerned state attorneys general are collaborating order to fight anti-democratic lawsuits, dangerous and false propaganda, and unconstitutional legislation.
→ Temporary event: He is playing center midfield because the starter is injured.

• not parallel
are not only consuming (verb)
is not parallel to
but also they are now home to . . . (clause)
Same analysis as that above applies here.
ELIMINATE E

The answer is B.

Comments

I am glad to see different approaches laid out in these answers, which range from good to excellent.

Versatility can be learned.

And today, the beginning of the end of two tragedies arrived. It's a good day.
Stay safe.