To determine the major product [X] of the given reaction, we analyze the reaction's mechanism and conditions. The starting compound is a benzophenone derivative, and the reaction involves the presence of an acid catalyst (H⁺).

The reaction likely proceeds through an acid-catalyzed rearrangement. Here's the step-by-step reasoning:

1. The carbonyl group (C=O) in the starting molecule is protonated by H⁺, increasing its electrophilicity.
2. Protonation facilitates a carbocation rearrangement. The acidic environment encourages a migration or a rearrangement of alkyl groups or carbon chains to stabilize the carbocation.
3. The methyl groups are likely involved in the rearrangement, potentially forming a more stable carbocation intermediate.
4. This rearrangement results in the formation of a new carbon-carbon bond, forming a cyclic compound which is stable under acidic conditions.
5. Finally, deprotonation occurs, leading to the formation of the major product, which is a stable, rearranged cyclic compound.

The correct major product, based on these steps, is represented by the image below:

This reaction is an example of an acid-catalyzed ketalization or cyclic ketone formation involving rearrangement.