在实验室使用剧毒药物必须由（）。
A.一人单独保管
B.二人轮流保管
C.二人共同保管
D.多人共同保管
参考答案：C
No one knew what because of the thick fog.
A．he had happened
B．had happened to him
C．had he happened
D．has happened to him
治疗行痹，应首选（）
A.乌头汤
B.薏苡仁汤
C.防风汤
D.宣痹汤
E.白虎加桂枝汤
