问题

t, _______ one cause that leads to theproblem
A:worked
B:had worked
C:are working
D:had been working
B:had worked
C:are working
D:had been working
正确答案是:
同类题型
All the teachers should try to make students know the______ of the study. Then they’ll study hard.
Did you tell Rose about the test? — Oh, no, I forgot. I call her now.[ ]
I don’t really work here; I ____ until the new secretary arrives
Forgotten something I can keep an eye on your kidsif you want to go and get it—______