2 Answers

A compound verb simply means there is more than one verb in the sentence. A verb is an action word so basically, in order for a sentence to have a compound verb it needs to be telling two things that the subject did.

Example:
Katy laughed and cried during the film.
"laughed and cried" would be the compound verb. It is saying she did more than one thing, she laughed and she cried.

The children played, ate, and napped at the day care.
The children did three things at the day care. The compound verb is played, ate, and napped.

As the others have stated, the helping verb can also contribute to a compound verb but that is a getting a little more complicated. What I have explained here is an easier way of looking at it. Helping verbs are another way of creating a compound verb so both are correct answers.

Too complicated for me