4. He usually ______ (play) football on Saturdays.

Explanation:

The word 'usually' indicates a habitual action, which is expressed using the present simple tense.

Solution:

For the third person singular subject 'He', the present simple tense form of the verb is the base form plus '-s' or '-es'.

1. Subject: He (third person singular)
2. Main verb: play + s = plays

Answer: plays