Don’t open the door to strangers;it’s not________.
— _____ do you go swimming with your father, Jane? —About once a week. A. How long B. How many times C. How often
Peter will take part in the boys’_____ tomorrow. A.800-meter race B. 800-meter races C. 800- meter- races
— What should we do to prevent the flu? —We should keep our rooms_____ and the air fresh all the time. A. cleaning B. cleaned C. clean
— When did your school hold the sports meet? —Last week. And I _______ the high jump. A. joined B. took part in C. will join
— Must we go to see a doctor at once when we have the flu? —No,_____. A. we mustn’t B. we shouldn’t C. we don’t have to