问题 选择题

设NA为阿伏加德罗常数,下列叙述中,正确的是 [ ]

A.2.9 g 2CaSO4·H2O中含有的结晶水分子数为0.02NA

B.1 mol过氧化钠中所含的阴离子数为NA

C.同温同压下,原子数均为NA的氢气和氦气具有相同的体积

D.电解精炼铜时,若阴极得到电子数为2NA个,则阳极质量减少64 g

答案

答案:B

单项选择题
阅读理解

第三部分:阅读理解(共12小题;每小题2分,满分24分)

请认真阅读下列短文,从每题所给的A、B、C、D四个选项中,选出最佳选项,并在答题卡上将该项涂黑。

Few people realize that there is a big difference between formal English and informal English. Formal English is used for most writing, and often in public speaking and formal meetings. It pays close attention to grammar rules, because if we use proper grammar, our meaning is often more precise. Also, on important occasions, we do not want to appear uneducated or to offend (冒犯) others, so we are very careful about how we speak. Informal English is used in speaking or writing to our friends and family. It often does not pay such close attention to grammar rules, because when we speak or write to them, we want our words to flow quickly. Also, with our friends and family, we are usually not so worried about appearing uneducated or about offending them by how we write or speak.

A big difference between formal and informal English is the use of contractions. A contraction is where we make a word shorter or where we put two words together and take away some of the letters. For example, instead of saying “do not”, many people say “don’t”. Using contractions in our speech is fine because it sounds natural, especially when we speak to our friends. In formal writing, however, contractions are usually avoided because people might think that you have made a mistake, or that you do not know proper grammar.

In the same way we might make words shorter, in informal English we often make sentences shorter as well. For example, if someone asks you your name, you will likely answer with one word: your first name. However, in formal English we usually use complete sentences. For example, we might write “My name is John”. In most speaking, we may not need to use every word in a sentence because the person we are speaking to will probably still understand us. In most writing, however, every word in a sentence must be written out in order to make sure that we can be understood.

56. When we use formal English, _______.

A. we will offend others 

B. we will appear educated on important occasions

C. we needn’t pay more attention to grammar rules

D. we can express ourselves more directly and more quickly

57. What’s the meaning of the underlined word “precise”?

A. simple                    B. direct                     C. puzzling                 D. clear

58. Contractions are best used when we are _______.

A. speaking at a formal meeting                        B. speaking to our friends

C. speaking in public                                              D. writing an application (申请) letter

59. In speaking, we do not always use complete sentences because ______.

A. we do not care about grammar                    B. we do not want to sound stupid

C. we can still be understood                              D. we don’t want to waste time