Answer:
C. Swiftly
Step-by-step explanation:
The simile in sentence three is "Penelope sprinted like a cheetah." Well we already know that a simile is a figure of speech that compares two different things, by using the words "like" or "as". In this example, the narrator compares Penelope's speed, to the speed of a Cheetah. Cheetah's are generally very fast. The definition of sluggish, is slow moving or inactive. The definition of merrily, is in a cheerful way. And the definition of despairingly, is to have absence of hope. We can use these definitions, and context clues from the text to figure out that swiftly, is in fact the correct answer.