How many hours a day do you sleep?

The question asks about a habitual or regular action using simple present tense. 'I sleep 7 hours' is correct because it uses simple present to describe a repeated or habitual action. 'I have slept seven hours' uses present perfect tense incorrectly for a habit. 'I am sleeping 7 hours' uses present continuous, which describes what is happening right now, not a daily habit. 'I slept 7 hours' is simple past, referring to a single completed past action, not a regular pattern.