who's
US
UK who's contraction: colloquial, contraction (who is)
SC 谁在
SC 谁是
Who's knocking at the door?
Who's Who n: US, informal (social elite)
SC 社会精英，名人 shè huì jīng yīng，míng rén
All the best families are listed in the Who's Who.
who's who expr: (identities)
SC 身份 shēn fèn
TC 身份
TC 身份
I'm not sure who's who in these old family photos.