It is reported that in our country cities __________ heavy air pollution that is 30 percent above the national standard or higher should try to meet standards by 2030.
________the working efficiency, the boss allows the employees to have a coffee break.
Only when he read this novel for a second time ________ to appreciate its beauty.
I ________ the boy to save the money, but he would not listen to me.
--- And then the ________ wind blew the roof off. --- Oh, you must have been ________.
Could people become infected ____ HIV by swimming in a pool or sitting in a bath?