Select the most appropriate option to fill in the blank.
He congratulated me ____________ my success.

Correct option is D

The correct option to fill in the blank is (d) on.
Explanation: The verb congratulate collocates with the preposition on to indicate the cause/reason for congratulations: congratulate someone on something. (Hindi: बधाई देना (किसी उपलब्धि पर))
Example: They congratulated her on winning the scholarship.
Explain why other options are incorrect:
· (a) of — shows possession/origin; not used after congratulate. (Hindi: का/की/के)
· (b) off — indicates separation/removal; irrelevant here. (Hindi: हटाना/दूर)
· (c) at — indicates place/time/target; not used for reasons of congratulations. (Hindi: पर/में)