申农和韦弗注意到传播和周围环境的关系，因此他们提出的传播模式中出现了一个新的环节，这个环节是（）

A．噪音

B．信号

C．反馈

D．信道

A RADIO SIGNAL FROM A DISTRESSED VESSEL AUTOMATICALLY DIRECTED TO A RCC GIVING POSITION，IDENTIFICATION，COURSE AND SPEED OF THE VESSEL AS WELL AS THE NATURE OF DISTRESS is known as（）.

A.Distress alert

B.Safety alert

C.Emergency alert

D.General alert