何种迁移理论认为迁移是无条件的、自动发生的（　） A．形式训练说 B．共同要素说 C

如图所示的四个圆形跑道，每个跑道的长都是1千米，A、B、C、D四位运动员同时从交点0出发，分别沿四个跑道跑步，他们的速度分别是每小时4千米、每小时8千米、每小时6千米、每小时12千米。问从出发到四人再次相遇，四人共跑了多少千米（）

A．14

B．15

C．16

D．17

D

The Internet has become part of teenage life.

A new report on 3,375 students aged from 10 to 18 in seven Chinese cities found that 38 percent of them believe they use the Internet often.

While most of them get useful information and use the Internet to help in their studies, some are not using it in a good way.

In order to help young people use the Internet in a good way, a textbook on good Internet behaviour (行为) has started to be used in some Shanghai middle schools this term. The book uses real examples to teach students all about good ways of using the Internet. The book gives useful advice such as it’s good to read news or find helpful information to study.

Some students also make online friends. But if you are meeting a friend offline, make sure your parents know. Teachers and parents all think the book is of great help. A teacher said the book would be a guide for teens using the Internet. She believes it will keep students away from bad sites. “Many students are using the Internet without guidance from their parents,” she said. “The book will teach students how to be a good person in the online world.”

68. The textbook mainly tells us ______.

A. why we should use the Internet    B. how to study using the Internet

C. how to use the Internet correctly   D. how to get help from others

69. What’s the attitude of teachers and parents towards the textbook?

A. They are against it.               B. They are for it.

C. They don’t care about it.          D. The passage doesn’t mention.

70. According to the passage, teenagers are NOT encouraged to ______.

A. read online news          B. go online 

C. find helpful information online

D. meet a friend offline without letting their parents know

71. From this passage we know that _______.

A. more and more students have given up visiting bad Web sites

B. schools and teachers begin to pay attention to students’use of the Internet

C. no more homework will be given in Shanghai middle schools

D. less and less information can be found on line

柴油机是工农业生产中常用的热机。已知某型号柴油机的效率为η，柴油的热值为q。将质量为m的柴油完全燃烧，能放出的热量Q＝______，这些热量通过该柴油机的转化对外所做的有用功W=_____。

企业开展国际直接投资的主要目的是为了获取股息或利息收入。

肺结核的可疑症状表现是什么？