为什么油路系统进油管细而出油管粗？

Most Americans enjoy moving from place to place. For example, they often drive their cars 120 to 160 kilometres away just to have dinner with a friend or even fly to London or Paris just to watch a football match. In some states only one person in five lives in a place for more than five years. One may be born in one city, and go to school in another. He may finish his middle school in two or three cities, and then go to college far across the country. When he begins to work, he may possibly move from job to job. Moving from one job to another, which is called “job-hopping”, can be seen in many places in the United States.

Job-hopping does good to workers because every change of a job gives them a chance to get better pay. And job-hopping also gives bosses the chance to get new ideas and skills from him or her.

小题1:From this passage, we can see Americans often travel to _______________.

A．have dinner with their friends

B．go shopping

C．watch a football game

D．enjoy themselves小题2:Which of the following is true?

A．About 20% of the people stay in one place for over five years.

B．Children have to finish middle school in one place.

C．People go to the nearest college.

D．When people begin to work, they don’t move any more.小题3:Job-hopping means “_______________”.

A．looking for a job

B．having a job

C．changing jobs often

D．losing a job小题4:In the USA job-hopping _______________.

A．is very popular

B．helps young people go to college

C．helps workers in traveling

D．helps students begin to work小题5:The writer thinks job-hopping _______________.

A．does good only to the workers

B．does good only to the boss

C．must be stopped

D．is helpful

绿色植物在光合作用过程中，每吸收44g二氧化碳，就能释放多少克氧气[ ]

A．30g

B．31g

C．32g

D．320g

肾小管性蛋白尿时尿中出现的蛋白为( )

A．白蛋白
B．前白蛋白
C．γ-球蛋白
D．β₂-微球蛋白
E．脂蛋白

过敏性紫癜最常见的类型是

A．紫癜型

B．腹型

C．关节型

D．肾型

E．混合型

简述HIV的结构，传播途径