题目内容

2．The first application of electron tubes were in（）.

A. radio
B. television
C. communication
D. broadcasting

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3．（）had surpassed radio for home use and entertainment.

A. Communication
B. Television
C. Video camera
D. Personal computer

4．Using echoes of radio microwaves, radar can detect（）.

A. a car
B. a ship
C. a plane
D. rain

5．The first electronic computer included 18,000（）and used 200 kilowatts of electrical power.

A. transistors
B. vacuum tubes
C. ICs
D. electronic components

6．A transistor is a semiconductor device used to（）electronic signals.

A. produce
B. amplify
C. reduce
D. switch