单三形式? "who" 是代名词,用来代替一个人或许多人都可以:"The pronoun who,in the English language,is the interrogative and relative pronoun that is used to refer to human beings." (1) "He is someone who is a great guy."(单) (2)"Who are they?" (复数) (3) "Who are those students in blue uniforms?"(复数)
