如图所示，小木块放在倾角为α的斜面上，受到一个水平力F（F≠0）的作用处于静止．则小

世界最大的湖泊是[ ]

A．青海湖

B．贝加尔湖

C．死海

D．里海

Most Americans enjoy moving from place to place. For example, they often drive their cars 120 to 160 kilometers away just to have dinner with a friend or even fly to Europe just for watching 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 attend a college far across the country. When he has entered business, he may possibly move from job to job. Moving from one job to another, which is called “job-hopping”, is a very common practice in the United States. Job-hopping is good to workers, because every change of a job gives them a chance to move up to a higher position and to get better pay. And job-hopping also gives bosses the chance to get new ideas and skills that different people bring to their companies and factories.

1. According to this passage, Americans often travel_______.

A. in order to have dinner with their friends

B. in order to watch football matches

C. to enjoy themselves

D. in order to find a new job

2. In some places in America, ________ for more than five years.

A. most people stay in one place

B. about 20% of the people live in one place

C. the owners of houses stay in one place

D. the owners of five house stay in one place

3. In the USA, job-hopping_______.

A. has become the custom (习惯)

B. has helped young people to attend to college

C. has helped students to enter business

D. has helped worker in traveling

4. The writer thinks________.

A. job-hopping does good either to workers or to the bosses

B. job-hopping does good neither to the workers nor to the bosses

C. little of the job-hopping

D. highly of the job-hopping

学校安全管理应当遵循的原则是什么？

（）是数据库系统的核心，用于数据库的建立、使用和维护。

A.硬件系统

B.软件系统

C.数据库管理员

D.数据库管理系统

光分纤箱可以在（）管辖的范围唯一命名。

A.站点

B.子区域

C.机房

D.光交接箱