To determine the major product [X] in the given reaction, we need to analyze the steps involved:

1. The starting compound features a sulfonium ion (SMe_2^+). Treatment with KOBut (potassium tert-butoxide) will likely lead to an elimination reaction. The tert-butoxide ion is a strong base and can deprotonate the hydrogen atoms adjacent to the sulfonium group, leading to formation of a double bond through elimination of the SMe_2 group.
2. Following the elimination reaction, Raney Nickel (Raney Ni) is a well-known catalyst for hydrogenation reactions. In the presence of ethanol (EtOH), Raney Ni will hydrogenate the alkene, converting the double bond into a single bond.

Given these transformations, the reaction proceeds through the following steps:

1. Elimination to form an alkene.
2. Hydrogenation of the alkene to form a saturated compound.

Looking at the options, the major product [X] can be identified by these transformations. The correct structure from the options is:

This product is obtained after the described elimination and hydrogenation steps.

Therefore, the major product [X] is the structure shown above, which matches the given correct answer.