Take a look at the sentence again:
When Diane takes her beagle for a walk, Santana enjoys sniffing for edible
garbage, __________, and lunging at squirrels.
The blank requires a gerund phrase. You chose howls at bicyclists, which includes the simple present tense and thus causes a parallelism error. Before you continue, review the rules for parallel structure.
Go back to the sentence to try again.