Answer:
The subject is gum, and the verb is chewing, so the answer is C
Step-by-step explanation:
We know this because the sentence is talking about colorful gum, meaning it is the SUBJECT of the sentence, and, we know that "to chew", or "chewing" is a verb. Based on these facts, we can conclude that the subject is gum, and the verb is chewing.
Hope this helps! :)