By seeing these options please answer the following question :-
assertion- ammonium Hydroxide is a weak base.
reason-then of phenolphthalein becomes pink in NH2 OH.

Dear student,
The correct option is (c) 
Reason:  Ammonium hydroxide is a weak base as it ionizes partially in water but due to the lesser number of OH^- ions Phenolphthalein can not change its colour in aq. the medium of ammonium hydroxide.
Regards