Take a look at the passage again:
Raja knew that his roommate Tina had cupcakes hidden in the apartment.
He looked everywhere. Including in the clothes
hamper, on top of the bookcases, behind the sofa—even under his own bed!—all
to no avail.
You chose the second part, He looked everywhere. This part has a main clause: He is the subject; looked is the verb. A fragment will not have a main clause. And remember, fragments don't have to be the shortest part!
Go back to the passage to try again.