人们在虚拟现实中的一切体验归结到最后都是一种（）体验。A、精神 B、物质 C、能量 D、信

下列哪些属于求职面试时应注意的礼仪？（）

A.进房先敲门

B.眼睛平视，面带微笑

C.边说话边整理头发

D.说话清晰，音量适中

1895年11月8日，德国物理学家威·康·伦琴在实验室内研究阴极射线管放电现象时，发现用黑纸包着的照相底片感光了。用黑纸包着的阴极射线管通电后，发现在其附近的一块涂有铂氰化钡的纸屏上发出绿色荧光，关闭电源，荧光消失。根据上述现象，伦琴推测，一定是从阴极射线管发出的一种新射线，并发现这种射线具有一定的特性，为此，他把这种未知射线起名为X线。X线的产生原理是高速电子和靶物质相互作用的结果。在真空条件下高千伏的电场产生的高速电子流与靶物质的原子核和内层轨道电子作用，分别产生了连续X线和特征X线。高速电子和靶物质相互作用过程中，将会发生碰撞损失和辐射损失，最终高速电子的动能变为辐射能、电离能和热能。三种能量的比例随入射电子能量的变化和靶物质性质的差别而不同。

影响连续X线产生的因素是（）

A.靶物质

B.管电流

C.管电压

D.高压波形

E.以上都是

在反应SO₃+H₂O═H₂SO₄中，反应前后发生改变的是（　　）

A．分子总数

B．原子总数

C．质量总和

D．质子总数和中子总数

Government officials reported three new cases of mad cow, bringing the total so far this year to 99. Last year, France recorded just 31 cases of the mad cow disease. The rising numbers are in part (1) a new testing program that focuses on cows that are most (2) . That program has (3) 39 cases. But still 60 new cases were identified in the usual way, (4) were found in 1999. Many scientists (5) that this year, five years after safety precautions were (6) , the number of cases would be (7) .

The rise in cases has (8) some scientists to question whether the disease can be transmitted in ways not yet understood. Scientists are still (9) the disease, first recognized in cows in 1986.

It appears that it is not caused by a bacteria, virus or fungus, but (10) infectious particles called prion, perhaps (11) a virus or other agent. The disease kills cells in the brain, (12) it spongy and full of holes.

France has taken more steps to (13) safety than most European countries, (14) refusing to take English beef (15) the European Union. But some scientists believe that France has not been (16) in imposing the ban on feed that (17) animal pans.

Some French officials hope that the sudden interest in mad cow disease will mean that French consumers will become educated about it, thereby recognizing that French beef is actually (18) controlled. Every cow is given a passport at birth, and extensive information about its parentage and (19) it was raised must be (20) to any slaughterhouse. When a diseased animal is found, the entire herd is destroyed.

5（）

A.expect

B.expected

C.have expected

D.had expected

短路电流周期分量和非周期分量各是如何产生的？各符合什么定律？