Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planet-wide destruction.

So the scientists found two facts about the asteroid. These two facts are connected by “and”. The first fact begins with “that”. However, the second fact does not begin with “that”. This leads to parallelism error in the sentence.

A. and, if it strikes Earth, it can do tremendous damage to part of the planet but: Incorrect for the reason stated above.

B. and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would: Incorrect. Repeats the same parallelism error of Choice A.

C. and that, if it were to strike Earth, could do tremendous damage to part of the planet but would: Correct.

D. and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would: Incorrect. This choice has ungrammatical structure. The “if” clause is unnecessarily in passive voice. The “then” clause is still in active voice. This makes it seem that Erath could only partly damage the planet. This meaning is illogical.

E. and that, if it strikes Earth, it could experience a tremendous amount of damage but: Incorrect. The pronoun “it” in the “then” clause refers to “asteroid”, meaning that the asteroid could experience damage. This is certainly not the intended meaning of the sentence.

I read this explanation on the e-gmat forum and am posting it here for the benefit of the fellow students.
Hope this helps everyone.
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But in C, isnt the use of 'that' and 'it' redundant? both are referring to asteroid!

Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and that,< if it were to strike Earth>, could do tremendous damage to part of the planet but would probably not cause planetwide destruction

remove the sentence between commas and read.. then C makes sense.

that is about half a mile wide and that could do tremendous..

that is necessary to maintain parallelism and correct usage.

if it were to strike Earth , that would probably not cause planet wide destruction --> correctly describes the hypothetical situtation.


"if it were to strike Earth" --> i don't see the best way to rewrite this statement without using "it". If you can try it


and, if it strikes Earth, it can do tremendous damage to part of the planet but

I agree that in E .. "it" after comma is redundant.
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Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planetwide destruction.


A. and, if it strikes Earth, it can do tremendous damage to part of the planet but needs and *that*
B. and, if it would strike Earth, part of the planet could experience a tremendous
amount of damage but it would needs and *that*
C. and that, if it were to strike Earth, could do tremendous damage to part of the
planet but would
D. and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would passive voice, requires subjunctive to describe the possible event
E. and that, if it strikes Earth, it could experience a tremendous amount of damage but present tense "strikes" is not appropriate to describe the possible event

First recollect the IF... THEN .. structure for the following cases:

1. IF simple present THEN simple future.
2. IF hypothetical subjunctive THEN conditional (would / could etc.).


Now consider a sentence in the first structure:
If it strikes Earth, it will probably not cause planet-wide destruction.

How would you convert this sentence to a future event not likely to happen (i.e., the second structure):
If it struck Earth (OR if it were to strike Earth), it would probably not cause planet-wide destruction.

Note that "would" in the THEN clause is a grammatical requirement to match the IF clause. Therefore in this case "would probably" is not considered redundant.

In the previous example, there is no IF.. THEN.. structure to justify the use of "would". In such standard cases, "will probably" is correct.

Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planet-wide destruction.

(A) and, if it strikes Earth, it can do tremendous damage to part of the planet but
correct structure That X ,and That Y - parallelism issue : Incorrect

(B) and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would
same as A : Incorrect
(C) and that, if it were to strike Earth, could do tremendous damage to part of the planet but would
Correct structure 'That X ,and That Y' & use of 'were' for hypothetical situation is correct.
(D) and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would
use of simple present in If.. clause for hypothetical situation is wrong : Incorrect
(E) and that, if it strikes Earth, it could experience a tremendous amount of damage but
'It' has antecedent issue . Asteroid or earth ; use of simple present in If.. clause for hypothetical situation is wrong : Incorrect


Experts pls. comment

daagh Skywalker18 AjiteshArun
I just wanted to know about the if else construction in OA: C
isn't it required before could ?

No, because in this construction, the that does what something like an it would normally do in a different construction. Look at what that part of C says:
... an asteroid... that, if it were to strike Earth, could do tremendous damage to part of the planet...

We have a relative clause here. Let's try reading it without the if:
... an asteroid... that could do tremendous damage to part of the planet...

Here the verb could do takes that as its subject. We can't supply another subject like it here. Take a look at the following sentence and check whether it sounds good:
... an asteroid... that it could do tremendous damage to part of the planet...

Now let's attach an if to include the conditional:
... an asteroid... that could do tremendous damage to part of the planet, if it were to strike [the planet]...

Option C just shifts the if clause to the beginning of the that clause.
... an asteroid... that, if it were to strike [the planet], could do tremendous damage to part of the planet...

Another example:
A student who, if he studies hard, he can get a good score...
vs.
A student who, if he studies hard, can get a good score...
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