单项选择题

How many times is the indoor air more hazardous than the outdoor air

A．10 to 12.
B．12.
C．2 to 10.
D．2.
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单项选择题
Rabin announced new security measures on television ______.
A．after an emergency session of his inner security cabinet
B．before the emergency meeting
C．after two Arabs were shot dead
D．before two Israeli policemen were killed
填空题
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