问题 单项选择题

与单向链表相比,双向链表______。

A.需要较少的存储空间

B.遍历元素需要的时问较短

C.较易于访问相邻节点

D.较易于插入和删除元素

答案

参考答案:C

解析: 本题考查链表存储结构的基本特点。在单向链表中只能沿一个方向进行访问节点,而在双向链表中既可以向前遍历,也可以向后遍历。因此,双向链表较易于访问相邻节点。

单项选择题
单项选择题

How to protect children Web fans from unsuitable material on-line while encouraging them to use the Internet has long been discussed in the US.

For some parents, the Internet can seem like a jungle, filled with danger for their children. But jungles contain wonders as well as dangers and with good guides, some education, and a few precautions, the wilds of the Internet can be safely navigated. "Kids have to be on-line. If we tell our kids they can’t have access to the Internet, we’re cutting them off from their future, " said an expert.

Most kids have started to use search engines. Many of them are great for finding tons of interesting Internet sites, and they can also locate places where you might not want your kids to go. There are search engines designed just for kids. A certain software contains only sites that have been selected as safe. The most popular way to limit access would be to use what is known as a "content screener". But this can’t be wholly reliable, and the best thing parents can do is to talk to their kids and let them know what is OK or not OK to see or do on the Internet. Another way is that mum or dad is nearby when the child is surfing the Internet.

A few other tips

·Don’t put the PC in a child’s room but keep it in an area where mum or dad can keep an eye on things. That also makes the Internet more of a family activity.

·Ask your child what he or she has been doing and about any friends they make on-line.

·Tell your child not to give on-line strangers personal information, especially like address and phone number.

·And tell your children never to talk to anyone they meet on-line over the phone, send them anything, accept anything from them or agree to meet with them unless you go along.

The best way to protect children from improper material is()

A. to install (安装) a content screener on the computer

B. to buy some search engines for the children

C. to be nearby when they are surfing the Internet

D. to talk to the children and persuade them to tell right from wrong