单项选择题

The returning echoes the receiver picks up are ________.

A．clearly audible bleeps
B．inaudible to human ears
C．immediately passed on to headphones
D．filtered through the transmitter
<上一题 目录 下一题>
热门 试题

单项选择题
What is the usage of the Pony Express
A．To help people travel from coast to coast.
B．To train ridem for competition.
C．To transfer materials and messages.
D．To arrest criminals in the West.
单项选择题
How long did the Pony Express Exist
A．61 years.
B．6 months.
C．One year.
D．18 months.
相关试题