去甲肾上腺素可使长期服用优降宁的患者发生（）

A.使优降宁效果增强

B.血压剧降后剧升

C.血压剧升后剧降

D.血压剧降

E.上述均错误

There are many things in different areas _____ we can do to reduce the possible dangers of AIDS.[ ]

A. where

B. there

C. what

D. that