单项选择题

What is the most effective way to clean the air

A．To let out clean gas.
B．To take in harmful gas.
C．To use various plants.
D．To let the air flow freely.
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单项选择题
For what purpose does the pilot shut off all the engines
A．To find out exactly what happens.
B．To save fuel to fly longer.
C．To find out where the big stone is.
D．To fly even more slowly.
单项选择题
What is the security problem of MySpace according to Buchanan
A．There are too many complaints from net users.
B．Hackers’ attack of MySpace cannot be forbidden.
C．Parents cannot help checking children’s information.
D．It is easy for trouble-makers to do harm to children.
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