The question refers to an “above reaction sequence”, but the actual reaction scheme/image is not present in the prompt. Also, the listed options are shown only as:

• A:
• B:
• C:
• D:

with no chemical structures or names attached.

Because of this, the problem is incomplete: the identities of components $A$ and $B$ depend entirely on the missing reaction sequence and the full option statements.

Step-by-step assessment

1. To identify component $A$ and component $B$, we must inspect the given reaction pathway.
2. The prompt does not include that reaction sequence.
3. The options are also blank/incomplete, so even option-wise evaluation is impossible.
4. Therefore, a chemically valid derivation cannot be made from the information provided.

Conclusion

I cannot reliably determine the answer from the current prompt alone. Although the stored correct answer is marked as B, there is no way to verify it without the missing reaction scheme and option details.