Question

Is this book____you want to read? That's right. I like books about the planets and the sun.

A: the one what B:that C: the one
请问选什么，为什么？
Is this the book____you want to read?
Right. Can you lend it to me ?
A:/ B:the one C: the one that
请问选什么，为什么？

Answer 1

Is this book____you want to read? That's right. I like books about the planets and the sun.
【答案】B
首先，the one作为不定代词在主句中充当表语，同时又作定语从句的先词。该句还原成陈述语序后为This book is _____ you want to read. (the one)
Is this the book____you want to read? Right. Can you lend it to me ?
A:/ B:the one C: the one that
【答案】A
该句中先行词是book,关系代词代替book在从句中作宾语，故可省略。该句还原成陈述语序为：This is the book ____ you want to read.

Answer 2

C the one作is表语，也是先行词，接了一个省略引导词的定语从句you want to read
A the book作is表语，也是先行词，接了一个省略引导词的定语从句you want to read