The players _____ from the whole country are expected to bring us honor in this summer game. [ ]

A. selecting

B. to select

C. selected

D. having selected

采用抗原抗体反应对传染病进行诊断，抗原与抗体的比例为（）。

A.3﹕1

B.1﹕3

C.1﹕1

D.2﹕3

E.3﹕2