Whilereadingabook,________.A.thegirlcameinB.mymotherwascookingC.Ihearda

While reading a book, ________.A.the girl came inB.my mother was cookingC.I heard a knock on the doorD.the doorbell rang

C解析试题辨析
本题涉及到句子真正主语的问题．也就是说While reading a book中在后省略了I was，这样后面句子的主语就应该是I．因此

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