Answer:
C. Participle phrase
Step-by-step explanation:
A Participle is a verb which acts as an adjective, describing a noun or pronoun. We have the present and past participles. In the phrase example given, 'curious' serves as the participle which describes the 'thing'.This tells us that the object in question is eager to learn about something.
So, the word curious, serves as both a description and the action word which is what a participle phrase means.