——Is there any possible way to help them get rid of such a bad habit? ——To tell the truth

问题补充：

——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 on this problem.

A. worked

B. had worked

C. are working

D. had been working

答案：

A. worked

B. had worked

(答案→)C. are working

D. had been working

解析：考查时态。“有帮助他们改掉这种坏习惯的可行的方法吗？”“说实话，非常难。但是我们还正在研究这个问题。”根据句意可知，用现在进行时。故选C。