B
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 behavior 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.”
40、The textbook mainly tells us .
why we should use the Internet.
How to study using the Internet.
How to use the Internet correctly.
How to get help from others.
41、What’s the attitude（态度）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.
42、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
43、From this passage we know that .
A、more and more students have given up visiting bad 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 online
44、What’s the meaning of the underlined phrase “of great help” ?
A、helpful B、good C、bad D、usefully
=60000(元) (2)最低现金管理相关总成本==3600(元) 全年现金转换成本=
×300=1800(元) 全年现金持有机会成本=×6%=1800(元) (3)最佳现金持有量下的全年有价证券交易次数=360000/60000=6(次) 有价证券交易间隔期=360/6=60(天)