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问题 单项选择题

下列关于线程和进程的说法正确的是

A．进程结构的所有成分都在用户空间内

B．用户程序能够直接访问进程涉及的数据

C．线程是内核级的实体

D．线程结构驻留在用户空间中

答案

参考答案：D

解析： 本题考查线程和进程的概念。线程与进程在概念上是相关的，进程由代码、数据、内、核状态和一组寄存器组成，而线程是由表示程序运行状态的寄存器，如程序计数器、栈指针以及堆栈组成，线程不包括进程地址空间中的代码和数据，线程是计算过程在某一时刻的状态。进程是一个内核级的实体，进程结构的所有成分都在内核空间中．一个用户程序不能直接访问这些数据。线程是一个用户级的实体，线程结构驻留在用户空间中，能够被普通的用户级方法直接访问。

单项选择题

关于慢性肺心病急性加重期使用强心剂的指征，以下不正确的是

A．感染控制，呼吸功能改善，但仍有反复水肿的心力衰竭病人

B．以右心衰竭为主要表现，而无明显急性感染的病人

C．合并冠心病出现急性左心衰竭者

D．合并高血压性心脏病出现急性左心衰竭者

E．心率＞120次/分，有房性早搏者
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单项选择题

High school dropouts earn an average of $9,000 less per year than graduates. Now a new study dispels a common belief why they quit. It’s much more basic than flunking out.
Society tends to think of high school dropouts as kids who just can’t cut it. They are lazy, and perhaps not too bright. So researchers were surprised when they asked more than 450 kids who quit school about why they left.
"The vast majority actually had passing grades and they were confident that they could have graduated from high school. " John Bridgeland, the executive researcher said. About 1million teens leave school each year. Only about half of African American and Hispanic student will receive a diploma, and actually all dropouts come to regret their decision. So, if failing grades don’t explain why these kids quit, what does Again, John Bridgeland: "The most dependable finding was that they were bored. " "They found classes uninteresting; they weren’t inspired or motivated. They didn’t see any direct connection between what they were learning in the classroom to their own lives, or to their career aspirations. "
The study found that most teens who do drop out wait until they turn sixteen, which happens to be the age at which most states allow students to quit. In the US, only one state, New Mexico, has a law requiring teenagers to stay in high school until they graduate. Only four states: California, Tennessee, Texas and Utah, plus the District of Columbia, require school attendance until age 18, no exceptions, another researcher, says raising the compulsory attendance age may be one way to keep more kids in school.
"As these dropouts look hack, they realize they’ve made a mistake. And anything that sort of gives these people an extra push to stick it out and it through to the end, is probably helpful measure. "
New Hampshire may be the next state to raise its school attendance age to 18. But critics say that forcing the students unwilling to continue their studies to stay in school misses the point—the need for reform. It’s been called for to reinvent high school education to make it more challenging and relevant, and to ensure that kids who do stick it out receive a diploma that actually means something.

According to the passage, which state has a law requiring school attendance until they graduate

A．New Hampshire
B．Utah
C．New Mexico
D．The District of Columbia
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