Sentence Correction (SC) | Re: The Mars Exploration Program

A is out since when we use whether the "or not" state is already intended.
B is out since the meaning and parallelism changes.

C- Seems to be okay. We have correct modifiers, verb, and parallelism. So hold.

D. to help to determine is wordy. Just to help determine is good. So out.

E. use of singular verb is for plural subject goals is wrong.

So I go with option C.