汽车刹车后继续向前滑行，是因为______，速度越来越慢是因为______．

下列何种因素与超声图像分辨力无关（）

A.发射超声的频率高低

B.发射超声的重复频率

C.发射超声的脉冲宽度

D.探头的宽度与声束的宽度

E.仪器对声束的聚焦性能

WLANs are increasingly popular because they enable cost-effective connections amongpeople, applications and data that were not possible, or not cost-effective, in the past.For example, WLAN-based applications can enable fine-grained management of supply and distribution ___24___ to improve their efficiency and reduce ___25___. WLANs can also enable entirely new business processes. To cite but one example, hospitals are using WLAN-enabled point-of-care applications to reduce errors and improve overall ___26___ care.WLAN management solutions provide a variety of other benefits that can be substantial but difficult to measure. For example, they can protect corporate data by preventing ___27___ through rogue access points. They help control salary costs, by allowing IT staffs to manage larger networks without adding staff. And they can improve overall network management by integrating with customers’ existing systems, such as OpenView. Fortunately, it isn’t necessary to measure these benefits to justify investing in WLAN management solutions, which can quickly pay for themselves simply by minimizing time-consuming ___28___ and administrative chores.

26（）

A.finance 

B.patient 

C.affair 

D.doctor

有一个学生选课的关系，其中学生的关系模式为：学生（学号，姓名，班级，年龄），课程的关系模式为：课程（课号，课程名，学时），其中两个关系模式的键分别是学号和课号，则关系模式选课可定义为：选课（学号，【5】，成绩）。

串联回路中，各个电阻两端的电压与其阻值成正比。

一国的国际收支中，计入资本和金融账户的是（）

A．从获得的国际援助 

B．对国外的直接投资 

C．对国外投资者发放红利 

D．从国外进口的机器设备