Review the passage:
Rocking and thrashing like a wild horse that cowboys had lassoed.
The washer complained about its overloaded tub.
At the other end of the Laundromat, Bobby quietly read an old magazine,
pretending that it was not his machine.
You chose the second part, The washer complained about its overloaded tub. This part has a main clause: Washer is the subject; complained is the verb. A fragment will not have a main clause.