A good many tourists,    ________with the natural beauty,    forgot their time to return.[ ]

A. impressing  

B. impressed

C. was impressed  

D. being impressed

伤寒患者病后可获得（）

A.暂时免疫

B.无免疫，可再次患病

C.较长时间的免疫

D.持久性免疫

E.一定的免疫力