Which words best help the reader understand the meaning of the word "compulsory" in the following passage:

"Bruce didn't want to help clean up the trash by the river but went anyway because the principal told him that since he chose to skip classes on Friday, his participation in the event would be compulsory."

Question 2 options:

clean up the trash by the river


the principal told him that since he chose to skip classes


Bruce didn't want to help


participation in the event