问题描述：
几道语法题
You can arrive in Beijing earlier for the meeting ( )you don’t mind travelling by air.
为什么用provided 不是until
Government cannot operate effectively ( )it is free from such interference.
为什么用unless 不用if only
His father had promised to buy him a computer ( )he behaved himself.
为什么用provided 不用after
You can arrive in Beijing earlier for the meeting ( )you don’t mind travelling by air.
为什么用provided 不是until
Government cannot operate effectively ( )it is free from such interference.
为什么用unless 不用if only
His father had promised to buy him a computer ( )he behaved himself.
为什么用provided 不用after
问题解答：
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