单项选择题

The highly efficient modern communication system began ______.

A．over a century ago
B．in the middle 1960s
C．in the late 1980s
D．in the year 1980
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单项选择题
The first two paragraphs tell us a true story of ______.
A．international cooperation via the Internet
B．how dangerous thallium can be to humans
C．how one can get help from the Internet
D．the girl's recovery from thallium poisoning
单项选择题
What is the energy source of this so-called solar-sail vehicle
A．Sunlight.
B．Nuclear.
C．Wind.
D．Electricity.
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