负外部效应的存在可引起（）
A.产量不足
B.产量过多
C.产量均衡
D.产量波动
参考答案：B
治痰饮水肿，夜盲眼目昏涩的药为
A．茯苓
B．苍术
C．泽泻
D．厚朴
E．地肤子
He made up his mind to devote his life _____ pollution ______happily．
A．to prevent; to live
B．to prevent; from living
C．to preventing; to live
D．to preventing; from living
