阴极灯丝发射电子经聚焦后在阳极靶面上的实际撞击面积称为实际焦点。有效焦点是指实际焦点在空间各个方向上的投影，是用来成像的X线面积。实际焦点在垂直于X线管窗口方向（过窗口中心）的投影称作标称焦点或有效焦点的标称值。标称焦点是有效焦点的一个特例，近似正方形。

关于有效焦点的叙述，错误的是

A:是指实际焦点在空间各个方向上的投影 B:标称焦点是有效焦点的一个特例 C:实际焦点面积要大于有效焦点面积 D:有效焦点在不同投影方向上形状和大小均不同 E:有效焦点越大，成像质量越好

阴极发射电子经聚焦后在阳极靶面上的实际撞击面积称为实际焦点。有效焦点是指实际焦点在空间各个方向上的投影，是用来成像的X线面积。实际焦点在垂直于X线管窗口方向（过窗口中心）的投影称作标称焦点或有效焦点的标称值。

关于实际焦点叙述错误的是

A:是电子实际撞击的面积 B:由主焦点和副焦点组成 C:聚焦槽与灯丝位置对焦点的形成有重要影响 D:副焦点大于主焦点时成像性能好 E:灯丝正面发射的电子形成主焦点

阴极发射电子经聚焦后在阳极靶面上的实际撞击面积称为实际焦点。有效焦点是指实际焦点在空间各个方向上的投影，是用来成像的X线面积。实际焦点在垂直于X线管窗口方向（过窗口中心）的投影称作标称焦点或有效焦点的标称值。

关于有效焦点叙述正确的是

A:在空间各个方向上的投影都一样 B:在不同投影方向上形状和大小均相同 C:有效焦点越小，成像质量越好 D:实际焦点面积要小于有效焦点面积 E:实际焦点越小，输出功率越大

Car Thieves Could Be Stopped Remotely

Speeding off¹ in a stolen car, the thief thinks he has got a great catch². But he is in a nasty surprise³. The car is fitted with a remote immobilizer, and a radio signal from a control center miles away will ensure that once the thief switches the engine   1  , he will not be able to start it again.

For now, such devices    2   only available for fleets of trucks⁴ and specialist vehicles used on construction sites. But remote immobilization technology could soon start to trickle down to ordinary cars⁵, and    3   be available to ordinary cars in the UK    4    two months.

The idea goes like this. A control box fitted to the car incorporates⁶    5    miniature cellphone, a microprocessor and memory, and a GPS⁷ satellite positioning receiver.    6   the car is stolen, a coded cellphone signal will tell the unit to block the vehicle’s engine management system and prevent the engine    7    restarted.

There are even plans for immobilizers    8   shut down vehicles on the moves⁸, though there are fears over the safety implications of such a system.

In the UK, an array of⁹ technical fixes¹⁰ is already making    9   harder for car thieves. “The pattern of vehicles crime has changed.” says Martyn Randall of Thatcham, a security research organization based in Berkshire¹¹ that is funded in part    10   the motor insurance industry.

He says it would only take him a few minutes to    11   a novice how to steal a car, using a bare minimum of tools¹². But only if the car is more than 10 years old.

Modern cars are a far tougher proposition¹³, as their engine management computer will not

  12   them to start unless they receive a unique ID code beamed out¹⁴ by the ignition key. In the UK, technologies like this    13   achieve a 31 per cent drop in vehicle-related crime¹⁵ since 1997.

But determined criminals are still managing to find other ways to steal cars. Often by getting hold of the owner’s keys in a burglary. In 2000, 12 per cent of vehicles stolen in the UK were taken by using the owner’s keys, which doubles the previous year’s figure.

Remote-controlled immobilization system would   14   a major new obstacle in the criminal’s way by making such thefts pointless. A group that includes Thatcham, the police, insurance companies and security technology firms have developed standards for a system that could go on the market sooner than the   15   expects.

词汇：    

immobilizer n．使车辆不能调动的装置
cellphone n．移动电话，手机
ignition / ɪɡˈnɪʃən / n．点火
trickle / "trɪkl / v．慢慢移动
immobilization / ɪˌməʊbəlaɪ"zeɪʃn / n．使车辆不能调动
burglary / "bɜ:ɡlərɪ / n．夜窃行为；盗窃

注释：

1. speed off：超速驾驶

2. catch：捕获物，猎获物

3. nasty：very unpleasant or annoying使人不愉快的；烦人的

4. fleets of trucks：卡车队。 Fleet：a group of vessels or vehicles owned or operated as a unit车队

5. trickle down to ordinary cars：慢慢地用到普通汽车上。 trickle：to move or proceed slowly or bit by bit慢慢地或一点一点地移动或前进

6. incorporate：to cause to merge or combine together into a united whole混合，合并到某一整体中

7. GPS：Global Positioning System全球定位系统

8. vehicles on the move：在行驶中的车辆

9. an array of：一群；一批

10. technical fixes：技术装置

11. Berkshire：a county of south-central England贝克郡，位于英格兰中南部

12. a bare minimum of tools：极少的工具。 bare：just sufficient；mere刚刚充足的；仅仅

13. Modern cars are a far tougher proposition：现代车远没有这么简单（偷盗现代车要困难得多 )。Proposition：a matter to be dealt with；a task任务，要处理的事务。

14. beam out：to emit or transmit发送，传送

15. drop in vehicle-related crime：涉及车辆犯罪案的下降。 drop：decrease下降

空13

A:have helped B:helped C:had helped D:was helped

北京时间8月13日凌晨4点对应格林尼治标准时几点（）？

A:8月13日10点 B:8月12日22点 C:8月12日20点 D:8月13日12点

一样本空间只含有等可能的样本点，而事件A与B各含有13个与7个样本点，其中4个是共有的样本点，则P(A|B)=______。

A:9/13 B:7/16 C:3/7 D:13/20

一样本空间只有等可能的样本点，而事件A与B各含有13个与7个样本点，其中4个是共有的样本点，则P(A|B)=______。

A:9/13 B:7/16 C:3/7 D:13/20