单项选择题

I'm sure the letter won't arrive in time ______ it is sent by air.

A．if
B．until
C．because
D．unless
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单项选择题
______ is generally accepted, economical growth is determined by the smooth development of production.
A．What
B．That
C．it
D．As
单项选择题
The term tsunami ______ the Japanese language meaning harbour and wave.
A．comes across
B．comes from
C．comes by
D．comes down
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