下列各句中均有一处错误,请找出并改正.

(  )1. That's wasteful to throw away waste paper.

           A          B             C               D

(  )2. Both Tony and Sam has been to the Great Wall.  

          A              B            C   D

(  )3. Everyone in the green school do something to help protect the environment.

                                                       A     B           C         D

(  )4. Those small factories cause too many pollution every day.

                                           A      B      C      D

(  )5. We should do our best to stop the factories from pollute the air.  

                           A                    B                         C     D

固定义齿修复的最佳时间一般是（）。

A.拔牙后3周

B.拔牙后4周

C.拔牙后6周

D.拔牙后2个月

E.拔牙后3个月