问题 单项选择题

一个算术表达式可以表示为一棵二叉树,每个叶节点对应一个运算量,每个内部节点对应一个运算符,每个子树对应一个子表达式。则下述二叉树对应表达式的后缀式(逆波兰式)为()。

A.A

B.B

C.C

D.D

答案

参考答案:C

解析:

二叉树对应表达式的后缀式(逆波兰式)就是该二叉树的后序遍历序列。

阅读理解

Students who say they never or hardly ever used dictionaries often speak English well but usually write poorly, because they make many mistakes.

The students who use dictionaries most do not learn especially well either. The ones who look up every new word do not read fast. Therefore they do not have time to read much. Those who use small two-language dictionaries have the worst problems. Their dictionaries often give only one or two words as translations of English. But one English word often has many translations in a foreign language and one foreign word has many translations in English.

The most successful students are those who use large college edition dictionaries with about 100,000 words but do not use them too often. When they are reading, these students first try to get the general idea and understand new words from the context. Then they reread and use the dictionary to look up only key words that they still do not understand. They use dictionaries more for writing. If they are not sure how to spell a word, or divide it into syllables (音节), they always use a dictionary. Also, if they think a noun might have an unusual plural form, they check these in a dictionary.

小题1: The writer thinks that        .

A.choose a good dictionary, and you’ll be successful in learning English

B.dictionaries are not necessary to the students who learn English

C.it is very important for students to use good dictionaries properly

D.using dictionaries very often can’t help to improve writing小题2:According to the passage, which of the following is wrong?

A.Dictionaries have little effect on learning to speak English.

B.Whatever new words you meet while reading, never use dictionaries.

C.Small two-language dictionaries have serious defects (缺陷).

D.Reading something for the first time, you’d better not use dictionaries.小题3:When in the reading does the writer advise students to use a good dictionary?

A.At the beginning of the reading

B.At the end of the reading

C.During the first reading

D.After the first reading小题4:This passage mainly tells us        .

A.students shouldn’t use small two-language dictionaries

B.what were the defects of small two-language dictionaries

C.why students should use large college edition dictionaries

D.what dictionary students should choose and how to use it小题5: Which is not mentioned in this passage?

A.How to make good use of a dictionary.

B.When to use a dictionary.

C.How to improve spoken English.

D.How to practise reading fast.

单项选择题