“safe speed” is defined as that speed where（）.

A.you can stop within your visibility range

B.you can take proper and effective action to avoid collision

C.you are traveling slower than surrounding vessels

D.no wake comes from your vessel

GSM系统由下列组成（）。

A.网络交换子系统（NSS）

B.基站子系统（BSS）

C.操作维护中心（OMC.

D.移动台（MS）