单项选择题

One of the extraordinary qualities of glass is that it can carry（）

A．sound signals
B．light signals
C．electrical signals
D．any signals

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热门试题

单项选择题

From the passage, you can tell that people prefer glass fiber cables to copper cables because （）

A．glass fiber is less expensive
B．glass fiber delivers messages directly
C．glass fiber is more up to date
D．glass fiber is easier to make

单项选择题

According to the passage the new telephone communication system （）

A．has been put into actual use
B．was first put into actual use in 1977
C．had been repeatedly experimented on before 1977
D．was put on experiment in 1977