单项选择题

One of the chief difficulties in accurate earthquake warning is that.

A．earthquakes may take place in anywhere possible
B．earthquakes may happen at any unexpected moment
C．most earthquakes take place simultaneously and unexpectedly.
D．the occurrence of earthquakes involves too many unforeseen factors .

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热门试题

单项选择题

What docs the word precursor in the context in Para. 3 mean

A．A man that may come before the happening of an earthquake.
B．The leading factor that may cause a series of events to occur.
C．Any meaningful sign that indicates some would- be happenings.
D．An event that may have symbolic or significant nature.

单项选择题

All the following statements are TRUE except that _____ according to the passage.

A．stronger materials will be developed to withstand serious earthquakes
B．seismic engineering has been greatly improved in the past years.
C．it won't be long before earthquakes can be predicted accurately.
D．something unpredictable may still happen beyond the expectations of the seismologist.