Take a look at the passage again:
Whenever Coach Moody sees behavior that she doesn't like—either on or off
the court. The members of the girls' basketball team pay during the next
practice. When Frankie was caught smooching her
boyfriend Larry in the hallway, everyone had to run two extra miles that
afternoon.
You chose the third part, When Frankie was caught smooching her boyfriend Larry in the hallway, everyone had to run .... This part has a main clause: everyone is the subject; had is the verb. A fragment will not have a main clause.
Go back to the passage to try again.