Here is the passage again:
Since the roof of Orlando Hall leaks, students know to check their seats.
To avoid soaking their pants in a puddle of water and then sitting in damp
underwear for an entire class.
You chose to use Punctuation Rule 5 to fix the problem:
Main clause + Ø + infinitive phrase.
The correction looks like this:
Since the roof of Orlando Hall leaks, students know to check their
seats to avoid soaking their pants in a
puddle of water and then sitting in damp underwear for an entire class.
Well done! You deserve that chocolate bar!