.--_________ will your parents come back to Shanghai?--Maybe in a month.
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.
—Could you tell me _____?—Sorry, I don’t know.