Answer:
The underlined word is pent-up, so the meaning is C. stored up.
Step-by-step explanation:
The noun pen can refer to a small enclosure for domestic animals. The verb to pen, thus, refers to the action of confining something in or as in a pen. The past participle form of pen is pent. Thus, the adjective pent-up refers to something that has been confined, repressed, held or kept inside.
In the context of the sentence "His pent-up energy found an outlet in a raucous game of tag football", the best option for a synonym or meaning to pent-up is C. stored up. It can actually substitute the adjective without any loss to the sentence:
"His stored-up energy found an outlet in a raucous game of tag football."