Fehling solution won’t react to both, acetone and benzaldehyde.

Fehling's solution is prepared by combining two separate solutions, known as Fehling's A and Fehling's B.

Fehling solution A is an aqueous solution of copper sulfate solution, which is deep blue.

Fehling's B is a colourless solution of aqueous of potassium sodium titrate (also known as Rochelle salt). The copper(II) complex in Fehling's solution is an oxidizing agent and the active reagent in the test.

Benzaldehyde does not contain alpha hydrogen so intermediate enolate formation does not take place. Thus, it does not react with Fehling's solution.

Ketone does not react with the Fehling's solution unless they are alpha-hydroxy ketones. Acetone is not alpha-hydroxy ketone so it will also not reduce the Fehling’s solution.