Which product is formed when the compound is treated with concentrated aqueous KOH solution?

The above reaction is an example of a Cannizzaro reaction.

A Cannizzaro reaction is a redox reaction in which two molecules of an aldehyde are reacted to produce primary alcohol and a carboxylic acid under the presence of a hydroxide base. There should be no alpha hydrogen (hydrogen attached to alpha carbon) as there will be no enolization and aldol condensation.

Benzaldehyde does not have an alpha hydrogen.

Thus, the product is a primary alcohol and potassium benzoate.