Fill in the blank: “I congratulated him _______ his success.”
Fill in the blank: “I congratulated him _______ his success.”
(A) for
(B) on
(C) at
(D) over
"I congratulated him on his success." The preposition that you should use when you tell someone that you’re congratulating them is "on", no matter what you’re congratulating them for. So, "on" is used when you’re praising someone for something they have achieved.