Sentence Correction

Through analysis of a microsite, which is a small area containing many fossils, a paleontologist can reconstruct a local ecosystem as it had been millions of years ago.
A. it had been
B. it might have been
C. it was
D. if during a time
E. though it were

my doubt: i fail to understand as why B is wrong here. how can we be so sure of something that was "million of years ago" ----->to bring that sense of "doubt" as how it was, i feel that "might have been" seems oki

The statement says the scientist 'CAN' construct. So we can assume that might have been is not the right option.
Looks like C is the correct answer. any OA for this question?