Take a look at the sentence again:
Neither the carrots rotting in the bottom bin nor __________ will make a
suitable side for the chicken you are planning to bake for dinner.
The blank requires a noun followed by a participle phrase. You chose the broccoli that is crusting over with freezer burn, which is a noun followed by an adjective clause. You thus have a parallelism error. Before you continue, review the rules for parallel structure.
Go back to the sentence to try again.