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．Eating out.B．Camping.C．Canoeing.D．Swimming.
A．Eating out.
B．Camping.
C．Canoeing.
D．Swimming.
单项选择题
A．It is being raised each year.B．It remains constant.C．It will reach sea level in 9,000 years.D．It is being lowered gradually.
A．It is being raised each year.
B．It remains constant.
C．It will reach sea level in 9,000 years.
D．It is being lowered gradually.
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