A. Suffrage and election. B. Checks and balances. C. The two politics to limit power and to control power. D. The dividing of functions among many entities. 参考答案:C 答案解析:第十三段Jefferson believed that the best practice for the avoidance of tyranny and the preservation of f
第23题: [单项选择]由多振子电子探头超声束形成的伪像称为() A. 混响效应 B. 切片厚度伪像 C. 旁瓣效应 D. 声影 E. 后壁增强效应 参考答案:C 答案解析:电子探头有多个压电晶片,每个晶片边缘都可以产生声强较低旁瓣,旁瓣的声速和各种传播特性与主瓣相同,探头是同时接收来自主瓣和旁瓣的回波信号,但超声仪在处理和显示回波信号时,不能将它们区分,而是叠加后全部显