现在完成时常和already, yet, sometime, always, never, ever, before, just等词连用, 也可以和包括现在在内的this morning, today, this week, this year等时间状语连用.
I have written 3 English e-mails today.今天我已经写了三封英文电子邮件了. I have painted six new pictures this week.这周我已经画了六幅新画. I have seen you before.我以前见过你.