关于定语从句的英语题两道

Question

1 I like this book ---- has a photograph of the author.
A of whose back cover
B which back cover
C whose back cover
D of which back cover
答案是C，为什么D不可以，CD有区别吗？

2 The river is not as clean as （what） it used to be.
老师说要what，我读不顺。。
类似的有
The friendly relationship between the two classes is developing as normally ---- it used to be.
A than what
B as that
C than that
D as what
答案是D，整个句子意思懂了，但不知为何要WHAT?
《省略句》在这行得通吗？

THANKS A LOTO(∩_∩)O~

Answer 1

1 whose +名词= the +名词+of which = of which + the +名词=which+the +名词+of

总之，用of which引导定语从句时要有定冠词the。双如：
The house whose roof is under repair belongs to Jim.
=The house of which the roof is under repair belongs to Jim.
=The house the roof of which is under repair belongs to Jim.
=The house which the roof of is under repair belongs to Jim.
2. what不能引导定语从句，它引导的是名词性从句（如主语从句、宾语从句、表语从句），且在从句中充当主语或宾语或表语。如：
She isn't what she was ten years ago. 她不再是十年前的她了。（这个was可以改成used to be)
Tell him what you like.告诉他你所喜欢的东西。
你所给的例句中, as是介词，后面引导宾语从句。

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Answer 2

1 whose +名词= the +名词+of which = of which + the +名词
2 第二题不是定语从句了。因为没有先行词的出现，what 在此做的是 used to be的表语，表示……的东西，人，地方。
这条河不再是像过去那样干净的河流了。