已知平面直角坐标系中,点O为原点,A(-3,-4),B(2,8).(1)求ABf

题型:解答题

问题:

已知平面直角坐标系中,点O为原点,A(-3,-4),B(2,8).
(1)求
AB
f坐标及|
AB
|

(2)求
OA
OB
考点:用坐标表示向量的数量积
题型:解答题

UML是一种面向对象的同一建模语言。它包括10种图,其中,用例图展示了外部参与者与系统内用例之间的连接。UML的外部参与者是指 (47) ,用例可以用 (48) 图来描述。 (49) 指明了对象所有可能的状态以及状态之间的迁移。协作图描述了协作的 (50) 之间的交互和链接。

(47)处填()。

A.人员

B.单位

C.人员或单位

D.人员或外部系统

题型:解答题

Now, there is a growing movement to pay the students in American schools---in some cases, even just for coming to class.

Students at one school in New Mexico can earn up to three hundred dollars a year for good attendance. In Baltimore, Maryland, high scores in state graduation tests can be worth more than one hundred dollars. And a New Jersey school system plans to pay students fifty dollars a week to attend after---school tutoring programs.

Schools that pay students can be found in more than one---fourth of the fifty states. Other schools pay students with food or other rewards.

Robert Schaefer is a public education director. He says paying students may improve performance in the short term, but students develop false expectations for the future. He sees a lack of long term planning in these programs because of the pressure on schools to raise test scores.

Public schools need to show improvement under the education reform law. Low---performing schools may lose their federal money; teachers and administrators(行政人员) may lose their jobs. Often these schools are in poor neighborhoods where getting students to go to school can be a continual problem.

Critics(评论家) say paying students sends a message that money is the only valuable reward. But some students say it makes school more exciting. And some teachers have reported getting more requests for extra help.

In two thousand four, the city schools in Coshocton, Ohio, launched a program. They wanted to see if paying elementary school students as much as one hundred dollars would help in passing the state exams.

Now, Eric Bettinger of Case Western Reserve University (EUCWRU) has reported mixed results. Math scores increased, but only white students were able to get paid. And there was no evidence of higher scores in reading, social studies and science. Official will decide later this year whether to continue the program.

小题1:Paying students who show improvement in tests __________.

A.has been done in most American schools

B.is becoming a growing practice in the USA

C.is not very popular with teachers

D.only aims at high scores at school小题2:According to the text, Robert Schaefer _____________.

A.is a very excellent teacher

B.thinks highly of paying students

C.thinks students will show improvement in study in the future

D.thinks people should make a careful plan for the paying program小题3:From the last paragraph we can see __________.

A.EBCWRU has got great success in its paying program

B.not all the students in EUCWRU have made progress in all subjects

C.only students who study math can get paid

D.EBCWRU will go on with the paying program小题4:The text is mainly written to _____________.

A.persuade teachers to give students more prizes

B.tell people how to become an excellent student

C.introduce something about American paying students program

D.explain the advantages of American paying students program

题型:解答题

根据物质分子大小进行分离可选用 ( )

A.硅胶
B.聚酰胺
C.离子交换
D.大孔吸附树脂
E.葡聚糖凝胶

题型:解答题

高掺性脱水引起()

A.血浆容量减少,组织间液容量减少,细胞内液容量正常

B.血浆容量减少,组织间液容量减少,细胞内液容量增多

C.血浆容量正常,组织间液容量减少,细胞内液容量减少

D.血浆容量减少,组织间液容量减少,细胞内液容量减少

E.血浆容量减少,组织间液容量正常,细胞内液容量减少

题型:解答题

生物转化中参与氧化反应最重要的酶是

A.加单氧酶

B.加双氧酶

C.水解酶

D.胺氧化酶

E.醇脱氢酶

更多题库