人称代词 it 只能用来代替无生命的东西。为什么在下列句子它代替有生命的 child 呢？这是否算是一种误用：
A child learns to speak the language of its environment.
儿童学习说他周围人说的语言。
child 和 baby 本身是个通性名词。父亲和母亲绝不会用 it 来指自己的孩子和婴儿，但是其他人，尤其在科技文章中却可以不区分它们的性别，而用 it 来替代，以避免使用 he or she。
What a beautiful baby—is it a boy? (LDCE) 多么好看的婴儿啊,他是男孩吗? (it 指未知的人)
At that moment another young man came into the shop. It was John's old friend Ron.
上句中的 another young man 明明是指人,为什么用 it 来指代他?这是困惑我很久的一个问题。请指点迷津。
当我们谈到某个人的身份(identity)时,我们可以用 it 来指人。it 意味着“这个不认识的人”(the unknown person):
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There's a knock at the door. Who is it? It's the milkman. 有人敲门。是谁呢？是送牛奶的。
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A tall man stood up and shook hands. It was Captain Lawrie. 一个高个儿站起来握手。他就是劳里上尉。
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It's Dr Stone, isn't it? She's usually good. 是斯通博士吗？她通常讲得很好。
由于 it 具有“the unknown person”的含义,所以它常常用于下列场合:
A. 有人敲门：
Who is it? It's me. 谁啊？是我。
B. 在电话里：
“Oh, by the way, there was a telephone call for you.” “Who was it?” “哦，顺便说一下，有你一个电话。” “谁打来的？”
C. 确认某人为何人：
Her face lighted when she saw who it was. 当她看出他是谁时,她的面孔亮了起来。请做下面的英语试题:
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Someone is knocking at the door, but who can ____ be? A. one B. he C. she D. it
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A knock on the door made him look up... But ____ was only the manager. A. this B. that C. she D. it(全国高考,91-54)