has tom come yet?yes he has already been here for 5 minutes填yet;already的原因
问题描述：
has tom come yet?yes he has already been here for 5 minutes填yet;already的原因
答
在现在完成时中,yet 用于否定句和疑问句末.
already 常用于肯定句中.
has tom come yet?是疑问句,所以用yet .
he has already been here for 5 minutes是肯定句,所以用already .