— I am going to Millie’s birthday party this evening, Mum.— ________. And remember to come back before 10.00 p.m.
_____ the environment is important for human beings.
This is the most beautiful park I have _____ visited.
Xi’an is a city with many places of interest and __ tourists come here every year.
—_____ you _____ your homework yet? —Yes, I _____ it ten minutes ago.
It’s necessary for you _____ exercise every day.