问题：
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 teachers________on this problem.
A．are working
B．had worked
C．worked
D．had been working
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 teachers________on this problem.
| A．are working | B．had worked | C．worked | D．had been working |
参考答案：