单项选择题

______ you understand this rule, you'll have no further difficulty.

A．Once
B．Unless
C．Only
D．Until
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______ did he give you much advice
A．In what
B．On what
C．What
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单项选择题
You must make ______ clear that no harm comes to her.
A．that
B．it
C．this
D．/
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