Which of the following will react at faster rate with acetone to give a product containing
C6H5NHNH2
The required structure can be obtained only when the reactant site has 2 available hydrogens. These are eliminated to form imine. Imines in which the nitrogen atom carries an electronegative group are usually more stable; think oximes and hydrazones.
So from the given options, we can first narrow down our choices by eliminating the primary and tertiary amines.
Among the remaining options, we pick phenyl hydrazine over aniline because it forms a more stable imine.