什么是货币政策传导的时滞及对货币政策效果有何影响？

The retired man donated (捐赠)  most of  his savings to the school damaged by the earthquake in

Yushu, ______ the students to return to their classrooms.     [      ]

A. enabling                  

B. having enabled      

C. to enable                      

D. to have enabled

My mother ______ English ten years ago.     [ ]

A. taught   

B. teached    

C. teach       

D. teaches

—         ?  

—I'm not feeling well. I have a cold.[ ]

A. Are you feeling well

B. What are you doing

C. Are you worrying

D. What's the matter

支气管胸膜瘘的常见症状有（）

A.咳嗽、咳痰

B.胸闷、呼吸困难

C.咯血

D.全身感染中毒症状

E.胸痛

为了方便司机的操作，放空管离司机室的距离不得超过（）m。

A.5

B.10

C.15

D.20