In the following reaction the major product [X] is

To determine the major product [X] of the given reaction, let's analyze the reaction conditions and the structural transformation involved:

The starting compound is a sulfoxide, which can undergo a thermal syn-elimination in the presence of acetic anhydride (Ac2O) and sodium acetate (NaOAc). This reaction typically results in the formation of a double bond, effectively removing the sulfoxide group through syn-elimination.
Given these reaction conditions, the major product [X] will be an alkene. Specifically, the syn-elimination of the SO group from the sulfoxide will lead to the formation of cyclohexene.
The following image represents the correct structure of the major product [X]:

Conclusion: The major product formed in this reaction is cyclohexene, and the correct answer is represented by the above image.
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