下列基于比较优势的农产品区域布局原则说法正确的是（）。
A.分散经营
B.生态适宜
C.环境安全
D.区际协调
参考答案：B, C, D
He said that light ______ much faster than sound. [ ]
A. has travelled
B. went
C. travels
D. travelled
丁字着药
