Which sentence contains an infinitive or infinitive phrase?

A.

After tonight, leave the dishes for me.

B.

This beetle keeps flipping onto its back.

C.

He is trying to find a pencil.

D.

To him, that dog is a best friend.

The answer is C.

To find the infinitive, look for the preposition "to" in front of the verb as you would find it in the dictionary. So, look for "to (verb) " instead of " (verb) ing" or " (verb) s" etc.

Answer C has "to find" in it, so it is the sentence you're looking for.