6．--- Is there any possible way to help them get rid of such a bad habit? --- To tell the

问题补充：

6．--- Is there any possible way to help them get rid of such a bad habit?

--- To tell the truth, it’s very hard. But we teacherson this problem.

A. are working

B. had worked

C. worked

D. had been working

答案：

(答案→)A. are working

B. had worked

C. worked

D. had been working

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