Which answer correctly identifies the underlined word in the sentence?

Sarah was so happy to have a part in the newly written play.

A.

infinitive phrase

B.

participial phrase

C.

participle

D.

infinitive

A phrase typically has more than one word: so it is not a phrase, either infinitive (an infinitive phrase here is: to have a part) or participial phrase.

Written is also not an infinitive: here the infinitive is "to have".

The correct answer is: participle, "written" is a past participle.