肝硬化产生腹腔积液最主要原因是（）
A.白蛋白不足
B.血氨产生过多
C.脾大，脾功能亢进
D.门脉压力增高
E.长期便秘
参考答案：D
Which of the following statements about a monopolist is least accurate（）
A. The monopolist faces a downward sloping demand curve.
B. Unlike an oligopolist, a monopolist will always be able to earn economic profit.
C. A profit-maximizing monopolist will expand output until marginal revenue equals marginal cost.
能够断开路径并将对象转换为曲线的工具是（）
A､节点编辑工具
B､擦除器工具
C､刻刀工具
