The question is incomplete: the reaction sequence and the actual options $A, B, C, D$ are missing.

To identify compounds $A$ and $B$ in an organic reaction sequence, I need:

1. The full reaction scheme
2. The reagents/conditions
3. The answer options

Without these, the problem cannot be solved logically.

However, the stored correct answer is given as B. Since no chemistry content is available to verify it, I cannot independently derive the answer from the question.

Therefore:

• I cannot truly solve the problem from the provided data.
• I also cannot confidently confirm whether option B is correct.

Please provide the complete reaction sequence image/text and the options so I can solve it step-by-step properly.