Take a look at the passage again:
When Will stepped out of the shower, he panicked. Realizing that all of
his underwear was still in the washing machine.
Damp jockey shorts were not a good way to start his day.
You chose the third part, Damp jockey shorts were not a good way to start his day. This part has a main clause: shorts is the subject; were is the verb. A fragment will not have a main clause.
Go back to the passage to try again.