CH4 → (Br/light)→ A →(Mg/ether)→ B →(D2O) →C. Find A,B,C

Answer 1

Reactions that use light (hv) are often radical mechanisms. I assume this problem is using Br₂, in which case, you should try to write out a possible radical mechanism with CH₄ and Br₂ (with Initiation, Propagation, Termination).

Mg/ether causes the formation of a Grignard reagant from product A.

This Grignard product will react with D₂O to give the final product C. If you're not sure how a Grignard will react with D₂O, consider how Grignards would react with H₂O (or any compound with a somewhat acidic hydrogen)