附着式自升塔式起重机在拆卸过程中，最后应留（）塔身。

A.1组

B.2组

C.3组

D.4组

- Could you tell me_______？

- Every four years.

A．how often the Olympic Games take place

B．when the Olympic Games are held

C．how often are the Olympic Games held

D．how often the Olympic Games were held