while（Echo)的功能是：等待Echo引脚出现（）才结束。

A、timeout

B、rexmt

C、binary

D、connect

A.Echo-Reply

B.Config-Nak

C.Echo-Request

D.Config-Request

A.Echo-Request

B.Echo-Reply

C.Config-Request

D.Config-Nak

A.Config-Request

B.Config-Nak

C.Echo-Reply

D.Echo-Request

A. Echo-Request

B. Config-Nak

C. Config-Request

D. Echo-Reply

From: Barbara Smallwood

Date: Monday, June 10th 20-- 08:42:17 A.M.

Subject: My schedule today

Dave,

I will be out of my office the (144) of the afternoon.

I will be in the south wing at a meeting from 1:30 until 3:00 and then I will be leaving for the day for an eye doctor's appointment. I did not finish double-checking the inventory numbers, but I left them with Margaret and she said she would get them done by 5:00 today. If you need me, do not (145) to call my cell phone: 333-4130.I will be checking e-mail (146) this evening as well.

See you tomorrow,

Barbara

(44)

A．rest

B．rests

C．rested

D．resting

B、print语句一次只能输出一个字符串，echo可以同时输出多个字符串

C、echo语句一次只能输出一个字符串，print可以同时输出多个字符串

D、echo语句前不能使用错误屏蔽运算符@

A、发送信号

B、接收信号

C、使能信号

A、触发脉冲

B、回波信号

C、环境温度

D、声波速度