The product of the following reaction is P . The number of hydroxyl...

The reaction proceeds via addition of Grignard's reagent ($PhMgBr$).

A Grignard reagent is an organomagnesium compound which can be described by the chemical formula ‘R-Mg-X’ where R refers to an alkyl or aryl group and X refers to a halogen.

When ${C}_{6}{H}_{4}CHOOH$ reacts with grignard's reagent  benzene along with an addition product is formed, which on further reaction with aq ammonium chloride gives ${C}_{6}{H}_{4}CHOOH$.

Here ${Ph}^{-}$ is a strong base which is extracting proton  from the reactant to give benzene.

The reaction is as follows,

Product P is benzene and it has zero hydroxyl group.