Developed for the European Space Agency in the 1990s, the rockets of the Ariane 5 class *did not yet prove their* reliability as of 2003.

A) did not yet prove their
D) had not yet proved their
E) has not yet proven their

Why is the answer D?

Why is the answer not E? Shouldn’t the answer include “proven”? Shouldn’t the answer say “has” because “as of 2003” indicate present perfect?

I’m not sure where you got this question, but I’d say the correct answer should say “HAD not yet PROVEN their.” 2003 was 12 years ago, so you want the past perfect.