Reaction of carbonyl cyclic diene with Grignard reagent
The given answer makes no sense with the substrate actually presented (but see "alternative possibility" below). You will get phenol.

If you start with phenol then, of course, the Grignard reagent just yanks off the hydroxyl hydrogen, only to have that hydrogen restored by the acid workup.  Now suppose you were to have the keto form cyclohexa-2,4-dien-1-one.  This tautomerizes to phenol precisely because the methylene hydrogen is more strongly acidic than it would be as a hydroxyl hydrogen in phenol.  So the Grignard reagent would if anything, go even faster for the methylene hydrogen in cyclohexa-2,4-dien-1-one than it would go the hydroxyl hydrogen in phenol - unless the ketone enolizes first.

That latter issue is academic.  Either way you get the same phenolate ion product, which upon acid workup gives phenol.

An alternative possibility

If the substrate structure in the question was misdrawn, then the given answer could be correct. Cyclohexa-2-en-1-one, with only one double bond in the ring conjugated to the carbonyl group, does not have any (relatively) strongly acidic hydrogens and so the Grignard reagent will add to the carbonyl group.  After acid workup the ketone is thereby converted to the tertiary alcohol in the given answer.

Grignard reagents do not react with carbon-carbon double bonds, so after adding to the carbonyl group or extracting an acidic proton that's all there is.