who " 谁”,如：Who is on duty today?
who's = who is " 是谁” 如：Who 's the tallest in your class.
whose 谁的,如：Whose book is it?
不明白的再问哟,请及时采纳,多谢!“”who " 谁”， 如： Who is on duty today?中的“on duty today“是什么？whois on duty today ? 今天谁值日？