问题 单项选择题

设栈S的初始状态为空。元素a,b,c,d,e,f依次通过栈S,若出栈的顺序为b,d,c,f,e,a,则栈S的容量至少应该为

A.3

B.4

C.5

D.6

答案

参考答案:A

解析: 根据题中给定的条件,可以作如下的模拟操作:①元素a,b进栈,栈中有 2个元素,分别为a,b;②元素b出栈后,元素c, d进栈,栈中有3个元素,分别为a,c,d;③元素 d,c出栈后,元素e,f进栈,栈中有3个元素,分别为a,e,f;④最后,元素f,e,a出栈,栈为空。
可以看出,进栈的顺序为a,b,c,d,e,f,出栈的顺序为b,d,c,f,e,a,满足题目要求。每次进栈操作后,栈中最多有3个元素,所以,为了顺利完成这些操作,栈的容量应至少为3。本题的正确答案为A。

阅读理解

A little under one-third of U.S. families have no Internet access and do not plan to get it, with most of the holdouts seeing little use for it in their lives, according to a survey released on Friday.

Park Associates, a Dallas-based technology market research firm, said 29 percent of U.S. families, or 31 million homes, do not have Internet access and do not intend to subscribe(预订)to an Internet service over the next 12 months. The second annual National Technology Scan conducted by Park found that the main reason why potential customers say they do not subscribe to the Internet is because of the low value to their daily lives rather than concerns over cost.

Forty-four percent of these families say they are not interested in anything on the Internet, versus just 22 percent who say they cannot afford a computer or the cost of Internet service, the survey showed. The answer “I’m not sure how to use the Internet” came from 17 percent of participants who do not subscribe. The response “I do all my e-commerce shopping and YouTube-watching at work” was cited by 14 percent of Internet-access users. Three percent said the Internet doesn’t reach their homes.

The study found U.S. broadband adoption grew to 52 percent over 2006, up from 42 percent in 2005. Roughly half of new subscribers converted(转变)from slower-speed, dial-up Internet access while the other half of families had no prior access.

“The industry continues to chip(击破)away at the core of non-subscribers, but has a long way to go,” said John Barrett, director of research at Parks Associates. “Entertainment applications will be the key. If anything will pull in the holdouts, it’s going to be applications that make the Internet more similar to pay-TV,” he predicted.

41. What does the underlined word “holdouts” in the first paragraph most probably mean?

A. some American families

B. those who hold out one’s opinions

C. those who have been surveyed

D. those who still haven’t access to the Internet currently

42. Many potential customers refuse to subscribe to the Internet mainly because _________.

A. they show too much concern about the cost B. they can find little value of it

C. they do most YouTube-watching at work D. the Internet doesn’t reach their homes

43. From the passage we can infer that ________.

A. It is not an easy job to transform those holdouts into the Internet users

B. people will adopt dial-up Internet access no more

C. many Americans enjoy doing e-commerce shopping at home

D. more than half of the population are using the Internet in 2005

44. According to John Barrett, what is the key to attracting more U.S. families to broadband service?

A. making the Internet look more similar to TV set

B. applying the Internet more to entertainment

C. providing more pay-TV programs

D. chipping away at the core of non-subscribers

45. Which is the best title for the passage?

A. Web develops with technology               B. The present situation of web

C. Many Americans see little point to web    D. It is urgent to promote web service

单项选择题