何谓OFDM？其中文全称是什么？OFDM信号的主要优点是什么？

在Visual FoxPro中，建立数据库表时，将年龄字段值限制在18～45岁之间的这种约束属于______完整性约束。

When you are reading something in English, you may often meet with a new word. What’s the best way to know it?

You may look it up in the English-Chinese dictionary. It will tell you a lot about the word: the pronunciation, the Chinese meaning and how to use the word. But how can you know where the word is thousands of English words? How to find it in the dictionary both quickly and correctly?

First, all the English words are arranged(安排) in the letter order. In the dictionary you can first see the words beginning with letter A, then B, C, D…. That means, if there are two words “desert” and “pull”, “desert” will be certainly before “pull”. Then if there are two words both beginning with the same letter, you may look at the second letter. Then the third, the fourth… For example, “pardon” is before “plough”, “judge” before “just”, etc.

Do you understand how to look up in the dictionary?

The dictionary will be your good friend. I hope you’ll use it as often as possible in your English study.

小题1:This passage is about______.

A．new words in writing

B．different dictionaries

C．the best way of reading

D．using an English-Chinese dictionary小题2:In the dictionary you may not find_______.

A．how to pronounce the word

B．the spelling of the word

C．who used the word first

D．how to use the word小题3:In an English-Chinese dictionary, the last word______.

A．begins with Z

B．begins with A

C．is a short one

D．is not often used小题4:Which group of words is in the right order in an English-Chinese dictionary?

A．perhaps, produce, plenty

B．straight, subject, surprise

C．century, center, business

D．foreign, entrance, headache小题5:In the passage the writer tries to tell us that_______.

A．we have to use a dictionary when we read something in English

B．an English-Chinese dictionary can tell us everything about a word

C．an English-Chinese dictionary can help us a lot in our English study

D．all English-Chinese dictionary are the same

读图甲和图乙，回答下列问题。

小题1:以下关于A市迁入人口的叙述，正确的是

A．人口迁移主要受自然因素的影响

B．迁入人口中女性数量多于男性可能会产生婚育方面的社会问题

C．该市外来人口大于本地人口

D．迁入人口中男性数量多于女性与该市产业结构有关小题2:迁入人口对该市的影响可能有

①缓解了人地矛盾                  ②促进了该市的经济发展 

③促进了该市的产业结构的调整      ④加重了该市基础设施的压力

A．①②

B．①③

C．②④

D．③④

首次发现两种中微子的时间是（）

A、1986年

B、1987年

C、1988年

D、1989年

商业用房贷款的楼盘必须满足的基本条件有：（）

A.项目合法，批件齐全

B.资金来源落实，且已按要求到位

C.开发商经营业绩好，无不良信用记录

D.市场定位准确，销售前景好