汞、银、砷作为酶的抑制剂主要与下列哪种基团结合()
A.羧基
B.羟基
C.巯基
D.咪唑基
E.氨基
参考答案:C
After Nanjing Youth Olympic Games Park ________, it will become a new tourist attraction.
A.completed
B.has completed
C.is completed
D.was completed
—Is this your bicycle, David?
—No, it's not _______. It's Helen's. [ ]
A. his
B. yours
C. mine
D. hers