The question refers to a reaction scheme, but the actual reaction image/structure and the option structures are missing. Only the labels A, B, C, and D are shown, without any chemical structures.

Because of that, the major product cannot be determined from the given text alone.

What is missing?

To solve this, I would need:

1. The starting compound structure
2. The reagent/conditions
3. The structures corresponding to options A, B, C, D

Without these, no chemical analysis of mechanism or product prediction is possible.

Conclusion

The problem is incomplete in its current form, so the answer cannot be derived reliably.

Since the stored correct answer is A, I cannot verify whether that is correct without the missing reaction scheme and options.