单项选择题

A．Helicopters have only been worked on by man since 1940.
B．Chinese children were the first to achieve flight in helicopters.
C．Helicopters were considered more dangerous than the early airplanes.
D．Some people thought they would become widely used by average individuals.
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单项选择题
A．Get into the car for safety.B．Wait patiently for the storm to develop.C．Head straight for the center of the storm.D．Collect information about a coming storm.
A．Get into the car for safety.
B．Wait patiently for the storm to develop.
C．Head straight for the center of the storm.
D．Collect information about a coming storm.
单项选择题
A．To make full use of the metals left.B．To protect the forest resources from being destroyed.C．To call for stopping using plastic meal-boxes.D．To awaken people to the environmental problems.
A．To make full use of the metals left.
B．To protect the forest resources from being destroyed.
C．To call for stopping using plastic meal-boxes.
D．To awaken people to the environmental problems.
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