—Peter, _____ do you visit your grandparents?

—Twice a month.[ ]

A. how long                  

B. how soon

C. how far                  

D. how often

经口对口人工呼吸时传播的细菌和病毒有（）

A.巨细胞病毒

B.艾滋病病毒

C.肝炎病毒

D.结核杆菌

E.幽门螺杆菌