Li Yan feel well today. [ ]
A. don't
B. doesn't
C. isn't
答案:B
锰酸钾(K2MnO4)中锰元素的化合价是
A.+7
B.+6
C.+4
D.+2
WTO中的专门协定有()
A.农业协定
B.与贸易有关的知识产权协定
C.纺织品与服装协定
D.电器产品协定
E.军工产品协定