There were so many cars held up by the heavy rain on the road that we had no        but to wait.  [      ]

A. alternative        

B. difference        

C. relation            

D. opposition

第三代头孢菌素具有以下特点（ ）

A．对肾的毒性最低

B．对G⁺菌的抵抗能力最强

C．对G^-菌的抵抗能力最强

D．对β-内酰胺酶最不稳定

E．透入血—脑屏障能力最强