单项选择题

According to the passage the new telephone communication system, ______.

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

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单项选择题

Which of the following statements best expresses the main idea of the passage

A. Glass is very useful because it has many unusual qualities.

B. Light signals have changed the use of glass in industry.

C. Glass fibres have reduced the cost of telephone communication.

D. The use of glass fibres to carry telephone message is an interesting new development.

填空题

Because I have so much work to do this afternoon I’m (able) ______ to go with you.