单项选择题

Which of the following does the passage mainly discuss

A．Missiles carried by submerged submarines.
B．Messages sent by submerged submarines.
C．Blue-green lasers used by submerged submarines.
D．The way to send a message to submerged submarines.

<上一题目录下一题>

热门试题

单项选择题

Which of the following is TRUE according to the passage

A．Water is a barrier to radio communication.
B．Lasers have found wide application in submarine communication.
C．Water absorbs all kinds of electromagnetic waves.
D．Very low frequency radio waves cannot be used to contact submarines.

单项选择题

Which of the following is NOT true of a laser system

A．It is able to make its way through water.
B．It is able to communicate with submarines at work.
C．Its beam reaches a submerged submarine with the help of an antenna.
D．It is able to carry more data than low frequency waves.