After some delay, the play went on without further problems. a. interjection b. preposition c. adverb d. conjunction

The answer would be preposition. "After some delay" is a prepositional phrase, and "After" is the preposition.

There isn't an interjection anywhere, which is an abrupt remark.There isn't an adverb, which is a modifier that modifies adjectives, verbs, or other adverbs and answers the questions "How? When? Where?"And there is no conjunction, which is a word that connects clauses.

:)