—Do you often see John        on the playground?

—No, but he is often seen        the guitar in the park.

A. run; play    B. running; to play    C. run; to play

治疗肺炎球菌肺炎时，首选的抗菌药物是（）。

A.庆大霉素

B.三代头孢菌素

C.青霉素

D.红霉素

E.四环素