Think which side has the most stable species

Draw all possible conjugate bases and idetify the most stable one. The most stable conjugate base corresponds to the most acidic proton

A) Draw out conjugate bases. Think about how atomic radius affects anion stability
B) Draw out all possible conjugate bases for each compound. Think how hybridization affects anion stability
C) Draw out conjugate bases. Think how inductive effect affects anion stability. Electron withdrawing groups stablize the anion, electron donating groups destabilize the anion.