问题 单项选择题

文法G=(VT,VN,P,S)的类型由C中的 (32) 决定。若GO=(a,b,S,X,Y,P,S),P中的产生式及其序号如下:

1:S→XaaY

2:X→Dqb

3:Y→XbXla

则GO为 (33) 型文法,对应于 (34) ,由GO推导出句子aaaaa和baabbb时,所用产生式序号组成的序列分别为 (35) (36)

(36)处填()。

A.13133

B.12312

C.12322

D.12333

答案

参考答案:C

解析:

形式语言的文法是一个4元组C=(VT,VN,P,S),其中VT是非空有限集,称为终端符集;VN也是非空有限集,称为变量集;P为产生式集;3为起始符,S∈VN。形式语言的文法按户的特性可分成正则文法、上下文无关文法、上下文有关文法和图灵文法4种类型,又分别称为3型、2型、1型和0型文法。所对应的可实现的自动机分别为有限状态自动机、下推自动机、线性有界自动机和图灵机。本题中给出的文法、生产式左部均是单个变量,因此是上下文无关文法。由此文法导出句子aaaaa的产生式号的序列及推导过程如下:

S→XaaY1→YYaaY2→aYaaY3→aaaaa 3

句子baabbb的推导过程为:

S→XaaY1→baaY2→baaXbx3→baabbx 2→baabbb2因而产生式序号的序列是12333和12322。

阅读理解

阅读理解。

     I once had my Chinese MBA students brainstorming on "two-hour business plans". I separated them

into six groups and gave them an example:a restaurant chain. The more original their idea, the better, I said.

Finally, five of the six groups presented plans for restaurant chains. The sixth proposed a catering (餐饮)

service. Though I admitted the time limit had been difficult, I expressed my disappointment.

     My students were middle managers, financial analysts and financiers from state-owned enterprises and

global companies. They were not without talent or opinions, but they had been shaped by an educational

system that rarely stressed or rewarded critical thinking or inventiveness. The scene I just described came

in different forms during my two years' teaching at the school. Papers were often copied from the Web and

the Harvard Business Review. Case study debates were written up and just memorized. Students frequently

said that copying is a superior business strategy, better than inventing and creating. 

     In China, every product you can imagine has been made and sold. But so few well-developed marketing

and management minds have been raised that it will be a long time before most people in the world can

name a Chinese brand.

     With this problem in mind, partnerships with institutions like Yale and MIT have been established. And

then there's the "thousand-talent scheme": this new government program is intended to improve technological

modernization by attracting top foreign-trained scientists to the mainland with big money. But there are worries

about China's research environment. It's hardly known for producing independent thinking and openness, and

even big salary offers may not be attractive enough to overcome this.

     At last, for China, becoming a major world creator is not just about setting up partnerships with top

Western universities. Nor is it about gathering a group of well-educated people and telling them to think

creatively. It's about establishing a rich learning environment for young minds. It's not that simple.

1. Why does the author feel disappointed at his students? [ ]

A. Because there is one group presenting a catering service.

B. Because the six groups made projects for restaurant chains.

C. Because all the students copied a case for the difficult topic.

D. Because the students' ideas were lacking in creativeness.

2. Which of the following scenes is NOT considered as lack of creation? [ ]

A. Papers were often downloaded from the Internet.

B. Students often said that copying is a preferable business strategy.

C. Students combine knowledge and critical thoughts to solve a problem.

D. Case study debates were written up as well as recited.

3. The underlined word "scheme" in the fourth paragraph means _____. [ ]

A. timetable

B. theme

C. project

D. policy

4. We can infer from the passage that _____. [ ]

A. China can make and sell any product all over the world

B. high pay may not solve the problem of China's research environment

C. cooperation with institutions has been set up to make a Chinese brand

D. the new government program are aimed at encouraging imagination

5. Which is the best title of the passage?  [ ]

A. Look for a New Way of Learning

B. Reward Creative Thinking

C. How to Become a Creator

D. Establish a technical Environment

单项选择题