先化简，再求值：x2-xx+1•x2-1x2-2x+1，其中x满足x2-3x+2

中心轴百分深度剂量（PDD）定义为（）

A.射野中心轴上某一深度处的吸收剂量与表面剂量的百分比

B.射野中心轴上模体表面的吸收剂量与参考点深度处剂量的百分比

C.射野中心轴上某一深度处的吸收剂量与模体最大深度剂量的百分比

D.射野中心轴上某一深度处的吸收剂量与参考点深度处剂量的百分比

E.射野中心轴上某一深度处的吸收剂量与空气中参考点处剂量的百分比

下列哪项诊断可能性最大

A．菌痢

B．宫颈撕裂

C． * * 壁血肿

D．会阴Ⅲ度破裂

E．肠胃炎

下列叙述中错误的是

A．软件测试的目的是发现错误并改正错误

B．对被调试的程序进行“错误定位”是程序调试的必要步骤

C．程序调试通常也称为Debug

D．软件测试应严格执行测试计划，排除测试的随意性

Defendants who can afford expensive private defense lawyers have a lower conviction rate than those who rely on court-appointed public defenders. This explains why criminals who commit lucrative crimes like embezzlement or insider trading are more successful at avoiding conviction than are street criminals.
The explanation offered above would be more persuasive if which one of the following were true

A．Many street crimes, such as drug dealing, are extremely lucrative and those committing them can afford expensive private lawyers.

B．Most prosecutors are not competent to handle cases involving highly technical financial evidence and have more success in prosecuting cases of robbery or simple assault.

C．The number of criminals convicted of street crimes is far greater than the number of criminals convicted of embezzlement or insider trading.

D．The percentage of defendants who actually committed the crimes of which they are accused is no greater for publicly defended than for privately defended defendants.

E．(E) Juries, out of sympathy for the victims of crimes, are much more likely to convict defendants accused of violent crimes than they are to convict defendants accused of "victimless" crimes or crimes against property.

TCP/IP是一个协议族，它的体系结构分4层：应用层、网际层、网络接口层和 (46) ，其中ARP协议属于 (47) 。为了在源主机和目的主机之间传送数据，IP协议需要确定源主机和目的主机是否在同一个网络中。

A．应用层

B．传输层

C．网际层

D．网络接口层