New buildings in earthquake-prone areas must be heavily reinforced or

B) is not wrong because of antecedent issue . Please read the followin:

If the intended antecedent of a single pronoun is clear (e.g., by virtue of parallelism and meaning), and
if there is no other reasonable antecedent, then don’t worry if there is an unreasonable antecedent some-
where else in the sentence.

Right: Supernovas destroy their immediate environments in vast explosions, but by syn-
thesizing heavy chemical elements, THEY provide the universe with the possibility
of biochemistry-based life as we know it.

Supernovas is the subject of the first clause. The they is also in subject position in the second clause,

which is parallel to the first clause. Even though there are at least two closer possible antecedents (en-
vironments and explosions), you know that they clearly refers to supernovas. The GMAT would consider

this sentence acceptable.

Thanks for sharing that! I actually recently went through my MGMAT guide however it's phrased differently and isn't as explicit. Which version of the MGMAT was this from?