21. We all like ______city because it is clean and beautiful.
A. us B. ours C. our D. we
22. —Do you know your mother’s birthday?
—Yes, it’s ______May 1st.
A. in B. on C. at D. to
23. —______I go out for fun, mum?
—I’m afraid you can’t. You must finish your homework first.
A. Must B. Need C. Should D. Can
