问题

few years, the coal workers theirlungs X-rayed to ensure their health

A:had worked
B:worked
C:is working
D:has been working

正确答案是：

同类题型

－ hours do you exercise every day －Two.

Nowadays, either 21st Century or other English newspapers _____ increasingly popular among us students.

Listen!Do you hear someone__________for help

ney he spent within a month _________more than 1,000 dollars

_____ I invite Jack to the party? 　 —Yes, it’ll be nice if you _____. 　