由设计单位或建设单位提出的技术修改或工程变更，采用（）

A、工程变更单

B、技术核定单

C、通知单

D、更改证明

The lifesaving signal indicating You are seen - assistance will be given as soon as possible is the（）.

A.vertical motion of white flags

B.vertical motion of a white light or flare

C.firing of a green star signal

D.None of the above