虚词（介词,连词,冠词,感叹词）在句中不充当任何成分.
但是,由介词构成的介词短语在句子中可充当补语或状语
如 I see him as my best friend. (补语)
I sent him a toy as his birthday prsent. (状语)
虚词（介词,连词,冠词,感叹词）在句中不充当任何成分.
但是,由介词构成的介词短语在句子中可充当补语或状语
如 I see him as my best friend. (补语)
I sent him a toy as his birthday prsent. (状语)