Review the passage:
Jonathon often tries to shock his composition instructor with weird paper
topics. Such as eating tarantulas or wearing women's underwear.
Professor Mauzy remains nonplussed, scandalized only
by the number of fragments in Jonathon's essays.
You chose the third part, Professor Mauzy remains nonplussed.... This part has a main clause: Professor Mauzy is the subject; remains is the verb. A fragment will not have a main clause.