自身免疫病最重要的基本特征是（） A.患者血中可测得高效价的自身抗体和（或）针对自身

以下内容正确的是（）.

A.丁型肝炎病毒必需和乙型肝炎病毒在一起才可以感染人

B.戊型肝炎是通过血制品传播的

C.戊型肝炎黄疸型较多

D.丙型肝炎危害最大

E.乙肝疫苗没有保护作用

学校升国旗时，当国旗匀速直线上升时，下列说法正确的是（　　）

A．旗受到的重力和绳对旗的拉力合力为零

B．旗对绳的拉力和绳对旗的拉力是一对平衡力

C．旗受到的重力和旗对地球的引力是一对平衡力

D．旗对绳的拉力和旗受到的重力是一对平衡力

井下机械设备齿轮的（）可以检修记录为依据进行检查。

A、磨损

B、点蚀

C、胶合

D、接触斑点面积

The relative decline of American education at the elementary-and high-school levels has long been a national embarrassment as well as a threat to the nation’s future. Once upon a time, American students tested better than any other students in the world. Now, ranked against European schoolchildren, America does about as well as Poland, behind at least 10 other nations. Within the United States, the achievement gap between white students and poor and minority students stubbornly persists.
For much of the last half century professional educators believed that if they could only find the right pedagogy, the right method of instruction, all would be well. Yet in recent years researchers have discovered something that may seem obvious, but for many reasons was overlooked or denied. What really makes a difference, what matters more than the class size or the textbook, the teaching method or the technology, is the quality of the teacher. Much of the ability to teach is innate-an ability to inspire young minds as well as control unruly classrooms that some people instinctively possess and some people definitely do not.