Solution:
The 1st step of the reaction is ozonolysis of cyclohexene. so, X will be adipaldehyde. The next step of the reaction is aldol condensation. adipaldehyde reacts with dil. and form aldol product cyclopent-1-ene-1-carbaldehyde.
Hence, the correct option (B) cyclopent-1-ene-1-carbaldehyde is correct option.