21. —Lucy, ______ apple on the table is for you. Remember to eat it.
—Thank you, Mum. We all know ______ apple a day keeps the doctor away.
A. an; an B. an; the C. the; a D. the; an
22.— ______ do most students do their homework every weekday?
—About two hours.
A. How far B. How long C. How often D. How much
23. It ______ Nick two hours ______ the room. Now it is clean and tidy.
A. takes; to clean B. takes; cleaning
C. spends; to clean D. spends; cleaning