The question refers to "the above chemical reaction", but the actual reaction scheme and the option structures for $A, B, C, D$ are not visible/provided in the prompt.

Because of that, the product $A$ cannot be determined from the given information alone.

Step-by-step analysis

1. To identify product $A$ in an organic chemistry reaction, we need:

   • the starting compound(s),
   • the reagent(s),
   • the reaction conditions,
   • and the option structures.

2. In the current prompt, only this text is available:

   • "Product 'A' in the above chemical reaction is :"
   • Options $A, B, C, D$ are blank.

3. Since the reaction itself is missing, no valid chemical deduction can be made.

4. Therefore, I cannot independently verify whether option $B$ is correct.

Conclusion

The problem is incomplete. Please provide the reaction scheme/image and the option structures so that I can solve it properly.