The major product formed in the following reaction sequence is

The reaction sequence described involves the conversion of an alkyne to a ketone through hydroboration-oxidation followed by halogenation and subsequent elimination. Let's break it down step by step:
Applying these steps to the given structure:

The starting alkyne is a terminal alkyne, which through the described sequence results in the formation of a 2-enone structure.
Thus, the major product formed is the enone shown in the provided image. This is the result of the bromination followed by elimination yielding a conjugated enone.
Conclusion: The major product is the conjugated enone, which corresponds with the correct answer option provided.
The major products X and Y in the following reaction sequence are 
The following conversion is an example of

The major product formed in the reaction given below is

In the following reaction

the major product [X] is
In the following reaction

the major product [X] is