1. I have two grammars, ______are of great use.

A. all of which

B. either of which

C. both of that

D. both of which

2. I want to use the same tools _______used in your factory a few days ago.

A. as was

B. which was

C. as were

D. which

3. Is _______ some German friends visited last week?

A. this school

B. this the school

C. this school one

D. this school where

4. I have bought two ball pens, _______ writes well.

A. none of them

B. neither of them

C. neither of which

D. none of which

5. All that can be eaten _______ eaten up.

A. are being

B. has been

C. had been

D. have been

答案解析：

1. D. 主句中的two表明不能选A.从句中的are表明不能选B. both of which用来引导非限制性定语从句.

2. C. as引导定语从句时通常构成such…as或the same…as固定搭配，其中such和same修饰其后的名词，as为关系代词，指代其前的名词引导定语从句。as在从句中可以作主语、表语或宾语。本题中as作从句的主语.

3. B. 为便于理解，改写本句话：This is the school that some German friends visited last week. 不难看出，作表语的the school是先行词。that引导了定语从句，因为that同时又作visited的宾语，所以被省略了。其它选项结构不对。

4. C. 因为是two ball pens, 并且定语从句的谓语writes是单数概念。因此，C是正确选项。

5. B. 本句话中，主句的主语是all, 为抽象概念。因此，其谓语应用单数的has been。关系代词that引导定语从句，并在从句中作主语。