When it ________ air pollution, Beijing faces the three “C”s, cars, coals and construction, which lead to Beijing’s thick air pollution.
His sister left home in 1998, and ______ since.
His ten years' hard work paid off and his dream ______ finally.
I'm amazed to hear from my school teacher again.Believe it or not, it's ten years ______ we metlast.
I didn't want ______ stupid but I just stood before my classmates with nothing in my head.
______time went on, the situation was improved.