Question

He started .... my sudden entrance. prepositions

Answer 1

in preposition are use in sentences
It hope help u

Answer 2

"The correct preposition that is best suited to be written in the blank is “at”

The correct sentence thus will be

He stared at my sudden entrance.

Here the speaker is talking about the stare which the other person is giving at him after he entered suddenly.

The preposition at is used to depict the sudden entrance of the speaker at which the person is staring.

"