His grandfather is seventy.  He's _____ good health. [ ]

A. at

B. on

C. with

D. in

小儿急性上呼吸道感染，最常见的病原体是（）

A.支原体

B.肺炎链球菌

C.溶血链球菌

D.真菌

E.呼吸道合胞病毒