Take a look at the passage again:
Day after day, thunderclouds rolled in during the early afternoon. Making
Madison's grass thrive from all of the water. Her
neighbors, however, prayed for a sunny afternoon so that Madison could finally
mow the jungle that was the front yard.
You chose the third part, Her neighbors, however, prayed for a sunny afternoon so that Madison could finally mow the jungle that was the front yard. This part has a main clause: neighbors is the subject; prayed is the verb. A fragment will not have a main clause.
Go back to the passage to try again.