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【单选题】在大地震发生前的瞬间，往往有地声、地光和地面轻微振动，先于强震动( )出现于地表，作为大震即将来临的预警信号，为人们提供了最后一次自救机会。
A.
几秒钟
B.
几分钟
C.
几十分钟
D.
几小时
【单选题】The Grand Canyon Standing on the rim of the Grand Canyon(大峡谷), gazing across this giant wound in the Earth’’s surface, a visitor might assume that the canyon had been caused by some ancient convulsion...
A.
it was caused by some ancient convulsion
B.
its presence is an embarrassment to the state of Colorado
C.
it looks like an injury on the Earth’s surface
D.
it has caused many visitors to injure themselves