问题补充：
The milu deer is deer that common in China long ago.
A. kinds of, used to be
B. a kind of, used to be
C. a kind of, to be used
D. all kinds of , to used be
答案：
A. kinds of, used to be
(答案→)B. a kind of, used to be
C. a kind of, to be used
D. all kinds of , to used be
解析：a kind of 意为:一种…, used to (do/be)意为: 过去经常.
