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.