Question

That's the only thing ________ can't be forgotten in my life.

1. A.
   that
2. B.
   which
3. C.
   who
4. D.
   /

Answer 1

A
本題是考查定語從句的引導詞。一般而言，當先行詞為人，引導詞就用who；當先行詞為物，引導詞用which；或者都可以用that。但是在以下幾種情況中，先行詞只能用that：
①先行詞是不定代詞時。如：She didn't forget anything that her mother had told her to buy.②先行詞被序數詞、形容詞最高級或被the last, the only, the very, the same等修飾時。如：This is the first book that I studied in the primary school.
Have you worked out the most difficult question that our teacher told us to do?
This is the very book that you want to borrow.③先行詞是被all, no, some, any, little, much等修飾時。如：They haven't got any dictionaries that we need.④先行詞是兩個或多個分別表示人和物的名詞時。如：He told us many interesting things and persons that we had never heard.⑤主句是以who, which引導的特殊疑問句時。如：Who is the man that you spoke to just now?⑥先行詞是主句的表語或關系代詞在從句中做表語時。如：China is no longer the country that it used to be.