Question

correct tense they (play) since four o' clock.

Answer 1

The correct tense would be “they have been playing since four o’clock.”

This is the present perfect progressive tense of the word “play.” It implies that the action is continuing, that is, it has not stopped yet.

When you want to signify that an action is still ongoing, or that it has not yet finished, then it is preferable to use the present perfect progressive tense of the word.