什麼情況用

has / have + p.p (past participle)是用在事情發生在過去,但影響到現在.
For example:
I' ve lost my passport.(=I can't find my passport now)
We' ve bought a new car.(=We have a new car now)

Sometimes we use already , just...That is because they mean the thing was past.
Such as:
just( 剛才,只是 )
My hair is wet.I have just washed it(=I wash my hair so it is wet now)