问题补充：
---Can you tell me something about metal ?
---Metal making machines and many other things .
A. used to
B. is used for
C. is used as
D. is used to
答案：
A. used to
(答案→)B. is used for
C. is used as
D. is used to
解析：此题重点考查be used to doing sth、used to do sth 、be used as和be used for doing sth四个个句型结构的区别和意义。be used to doing sth是习惯做某事，used to do sth表示过去常常做某事，现在不做了。be used as是把…用作…be used for doing sth表示被用来做某事。
