单项选择题

A．Microwaves are strange electric waves.
B．Microwaves travel in straight lines and do not follow the curve of the earth’’s surface.
C．There are not any wires to send microwaves.
D．We must amplify microwaves in relay stations.
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单项选择题
A．Quiet plants.B．Well-watered plantsC．Healthy plants.D．Thirsty plants.
A．Quiet plants.
B．Well-watered plants
C．Healthy plants.
D．Thirsty plants.
单项选择题
A．They give out faint cries.B．They make noises to drive away insects.C．They extend their water pipes.D．They become elastic like rubber bands.
A．They give out faint cries.
B．They make noises to drive away insects.
C．They extend their water pipes.
D．They become elastic like rubber bands.
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