Take a look at the passage again:
Struggling up three flights of stairs, her arms filled with the heavy texts
for four classes, her backpack loaded with notebooks and other supplies.
Jamala huffed and puffed. Never again would she
register for all of her classes back-to-back on the same days of the week.
You chose the third part, Never again would she register for all of her classes back-to-back on the same days of the week. This part has a main clause: she is the subject; would register is the verb. A fragment will not have a main clause.
Go back to the passage to try again.