填空题

Observation posts have been set up alongside the most dangerous craters to ______.

【参考答案】

to detect and warn people of imminent eruptions
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填空题
Hot mineral springs could be used ______.
单项选择题
A．It was made of aluminum.B．It wasn’t large enough.C．It wouldn’t move the wind.D．It was too heavy to put up.
A．It was made of aluminum.
B．It wasn’t large enough.
C．It wouldn’t move the wind.
D．It was too heavy to put up.
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