_______environmental damage is done, it takes many years for the ecosystem to recover.
| A．Even if | B．If only | C．While | D．Once |
34. When he knocked at the door, my mother was busy ____ supper.
| A．preparing for | B．in preparing |
| C．to prepare for | D．to prepare |
33. He waited until it was dark ____ nobody could see him clearly.
| A．so that | B．in order to | C．although | D．However |
31. We should think of ways to stop the waste from the factory _____ our living environment.
| A．being polluted | B．polluting | C．from being polluted | D．Polluted |
28. As far as I know, this man ____ risk anything than lose the ring for his wife.
| A．would rather | B．had better | C．preferred | D．would like to |
27. She locked her room _____ a thief would break into it.
| A．in case that | B．for fear that | C．in case of | D．for fear of |