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 first part, When Will stepped out of the shower, he panicked. This part has a main clause: he is the subject; panicked is the verb. A fragment will not have a main clause.
Go back to the passage to try again.