单项选择题
A．pretty B．crowded C．noisy D．wonderful
A．a hovercraft can not fly high because of the surrounding high-pressure air B．a hovercraft is as much in use as a plane C．a hovercraft "flies" with a greater speed than ships D．a hovercraft also has the problem of wave resistance
A．wonder what to do in the future B．pay no attention to the UN’s call C．take no measure in conservation D．should act quickly to answer the UN’s call