I am very grateful ______________ the dog. [ ]
A. at
B. of
C. to
答案：C
常用于消毒的紫药水是高锰酸钾（KMnO4）的稀溶液．KMnO4中锰元素的化合价是（ ）
A．+2
B．+6
C．+7
D．+4
Special attention should be _____ to air pollution wherever the factory will be built.
A．made
B．paid
C．taken
D．sent
