Question

I congratulated my friend ____ his success fill with preposition​

Answer 1

I congratulated my friend on his success.

Prepositions In English Grammar

• Prepositions are used in almost all the sentences because without them, a sentence will remain incomplete and will make no sense.
• These words are almost 150 in number and they are used as connectors to connect nouns and proper nouns with other parts of the sentence.
• We can also use prepositions to show time, location, and direction.
• Some examples of prepositions are to, by, from, upon, of, etc

So the right answer will be on.