苯妥英钠水溶液露置空气中可析出苯妥英而显浑浊，这是因为（）
A.被氧气氧化
B.与CO2形成的碳酸反应
C.水解
D.蒸发
E.脱水
参考答案：B
A good _______ must _______ well. He should communicate_______ other people to practice acting. [ ]
A. actor, act, with
B. act, act, and
C. actor, acts, with
D. acts, act, and
一个外加电压为U的R、L、C串联电路，其谐振频率为（）。
A、f0＝1／LC
B、f0＝1／ωLC
C、f0＝1／2πLC
D、f0＝1／2LC
