Every possible means _____ to prevent the air pollution, but the sky is still not clear. [ ]

A. is used

B. are used

C. has been used

D. have been used

女，45岁。有风湿性心脏病，二尖瓣狭窄，经常自觉气短，来医院诊为慢性心功能不全，并给予地高辛每日维持量治疗，但该病人不久发生强心苷中毒，分析原因可能是()

A.合用奎尼丁

B.合用呋塞米

C.合用维拉帕米

D.病人发生低血钾、低血镁

E.以上均可能