Review the item:
Waves that crash against the shore,
chanting monks, and chirping
birds are the sound files that Wendell most enjoys.
When you list grammatical items, you must use parallel structure. Here, chanting monks and chirping birds are both noun phrases, but waves that crash against the shore is a noun modified with an adjective clause, which wrecks the parallelism.
To fix the item, change waves that crash against the shore to crashing waves.