In the following reaction the major product [X] is

The reaction sequence given involves multiple steps that are common in organic synthesis. Let's analyze each step one by one:
Thus, the sequence of reactions transforms the starting compound to the major product, which is a conjugated cyclic diene.
The correct major product is represented by the following structure:

This choice corresponds to the correct transformation as per the reaction conditions 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