长句子如果在语法结构上平行，就会显得比较清晰和易于理解；在一个句子或者一组句子中，如果具有相同的语法结构并起相同语法作用的部分称为平行结构；
eg. It is important for engineers to think logically, to analyze carefully, and to make decisions realistically.

1.平行结构的用法

并列结构的成分必须结构相同，名词连着名词，动词与动词相连，从句和从句相连，动词相连的时候必须以相同的形式。而且在平行句中常常使用成对的关联词
比如：both...and, either...or, not only... but also, neither ...nor, not …but etc
1 Viruses carry either DNA or RNA, never both.
2 Either we go full speed ahead or we stop right here.
3 Clearly/Obviously, neither serological tests nor virus isolation studies alone would have been adequate.

4 Let us now look at parallelism not simply as a potential problem in structure, but also as an asset in effective writing style.
2.表达平行意义的语法结构
A) words or phrases单个词和词组的并列
1 If you want to earn a satisfactory grade in the training program, you must be punctual, courteous, and conscientious.
2 English academic writing has good content, clear organization, and effective language.

B prepositions or Prepositional phrases介词词组的并列
1 In matter of principle, stand like a rock; in matter of taste, swim with the current. ----Thomas Jefferson
2 Studies serve for delight, for ornament, and for ability. Their chief use for delight, is in privateness and retiring; for ornament, is in discourse; and for ability, is in judgment, and disposition of business.----Francis Bacon
读书足以怡情，足以博彩，足以长才。其怡情也，最见于独处幽居之时；其博彩也，最见于高谈阔论之中；其长才也，最见于处世判事之际。

C-Infinitives or Infinitive phrases.动词不定式的并列
1 To walk in the rain and to swim in the lake are two of my greatest pleasures.
2 They decided to begin again: to begin hoping, to begin trying to change, and to begin working toward a goal.

D- Gerunds or Gerundial phrases.动名词
1 Writing is a skill like driving, typing, or cooking.
2 I spent the day cleaning the house, reading poetry, and putting my life in order.

E-Clause从句并列

1 We are looking for engineers who can think logically, who can analyze carefully, and who can make decisions realistically.
2 The advantages of a table are that it can present numerical data more concisely than a text can and that it can provide more details than a graph can.
3 Although the car was highly rated and although the car was guaranteed, the engineer found many faults.
4-He was promoted because he was industrious, because he was punctual, and because he was willing to put in extra effort.

F- Sentences句子并列

1-History became popular, and historians became alarmed.
2-Should scientists go into research, or should they teach, or should they work in industry?

In brief, mass media, by offering topics and affecting the ways in which we discuss “the important issues”, have a strong influence on our perception of the truth, of the world or of the structure of our society. We have to admit that it has a role in our lives as a source of information, experiences, entertainment, amusement and relaxation.

People succeed not merely because they have one or more certain skills. However, if I have to choose one skill which is supposed to be useful to success, I think it should be the ability to convince or persuade others.

By convincing or persuading we get what we want from others. When we were children, we always managed to persuade our parents to buy us sugar candies; when we were in the high school, we had to persuade our classmates to play with us; when we applied for a job after graduation, we’d better be able to successfully convince the employer that we are qualified employees. Besides, some day, we will all have to convince a person whom we love that we are in deed outstanding husbands or excellent wives.

By convincing or persuading we become more and more sturdy and powerful. Nobody is capable of doing every thing perfect. By persuading others to cooperate with us, we can achieve much more than we could only by ourselves.

Harmful Effects of Watching Television

In a recent cartoon, one character said to another, “When you think of the awesome power of television to educate, aren’t you glad it doesn’t?” it is true that television has the power to educate and to entertain, but unfortunately, these benefits are outweighed by the harm it does to dedicated viewers. Television is harmful because it creates passivity, discourages communication, and presents a false picture of reality.

The Benefits of Television

We hear a lot about  the negative effects of television on the viewer. Obviously, television can be harmful if it is watched constantly to the exclusion of other activities. It would be just as harmful to listen to CDs all the time or to eat constantly. However, when television is watched in moderation, it is extremely valuable, as it provides relaxation, entertainment, and education.