The question appears to be incomplete.

1. The reaction scheme is missing.
2. The options corresponding to A, B, C, and D are also blank.
3. Without the actual reaction and option structures, it is impossible to determine what compound 'A' is.

So, from the provided data, the problem cannot be solved chemically in a valid step-by-step way.

However, the stored correct answer is given as B.

Since there is no reaction or option content available to verify independently, I cannot genuinely derive the answer from chemistry. Therefore, I cannot confidently agree with the stored answer on logical grounds.