I know you can rule out B and D immediately b/c
B: both the Br's and the Methyl's are on top of each other. no good
D: Is wrong because the methyls on the back are on the wrong carbon, one of them should be an H. and on the front, one of the H's should be a methyl
Now between A and C what I think is (this is just a guess b/c I would have picked C)
with C: you have a methyl and a Br interacting on both sides, and thats not good for stability
Whereas with A: you have only one set of methyl and Br interacting and even though there are two Br's interacting also theyre both small so its not a big deal
Do you have an explanation?