一、主谓一致的原则
主谓一致是指主语和谓语在人称和数上保持一致。一般遵循下列原则：
1. 语法一致原则：主语和谓语在人称和数上一致。主语是单数形式，谓语动词也采用单数形式；主语是复数形式，谓语动词也采用复数形式。
2. 意义一致原则：谓语的单复数取决于主语的意义。当主语形式上为单数，但意义上却是复数时，谓语根据意义用复数形式；当主语形式上为复数，但意义上却是单数时，谓语根据意义用单数形式。
3. 就近一致原则：谓语动词的形式与邻近的主语在人称和数上一致，即谓语动词的单、复数形式取决于最靠近它的主语的单、复数形式。
二、主谓一致的具体应用
1. 名词作主语
（1）集体名词作主语，如果表示整体概念，谓语动词用单数形式；如果强调个体，谓语动词用复数形式。常见的这类名词有army, audience, class, family, team, crowd, staff, government, enemy, committee等。有些集体名词如cattle, people, police等，通常看作复数，谓语动词必须用复数。如：
The army has advanced to the river.
The team are driving to the game in their own cars.
The police have been searching for Tom for years.
（2）单复数同形的名词作主语，应根据其意义来决定谓语形式。如：
The only means of communication between them was sign language.
All possible means have been tried.
（3）表示单数概念的复形名词（如学科、机构、书名、剧名等）作主语，谓语动词通常用单数。如：
Statistics is a principal course at the business college.
General Motors produces many different types of cars.
（4）trousers, shoes, chopsticks, sunglasses等名词作主语时，谓语动词通常用复数形式；但如果其前有a pair of, a kind of等时，谓语动词一般用单数。如：
These trousers are too large.
A pair of trousers is not enough.
（5）当名词短语的中心词为表示距离、金额、时间等的复数名词时，往往把这些复数名词看作一个整体，谓语动词用单数。如：
Seven kilometers was covered in two hours.
Two hundred dollars is a lot to me.
Ten minutes was given to prepare the answer.
（6）“more than one / many a 单数名词”作主语，谓语动词通常用单数形式；“more 复数名词 than one”作主语，谓语动词通常用复数形式。如：
More than one person has been involved in this.
Many a student has seen the film.
More boxes than one have been used at the station.
（7）“分数或百分数 of 名词”构成的短语作主语时，谓语动词的单复数取决于of后名词的数。如：
Only one third of the homework was finished yesterday.
Three fourths of the students come to school on time every day.
2. 代词作主语
（1）代词each, either, neither, another以及复合不定代词作主语时，谓语动词用单数。如：
Each student has a dictionary in our class.
Anyone who is over sixteen is allowed in.
（2）关系代词who, that, which等在定语从句中作主语时，谓语动词的数应与先行词的数一致。如：
Don’t you know the people who live next door?（先行词是people）
My wife, who is out at the moment, will phone you when she gets back.（先行词是My wife）
（3）all, most, none, some等作主语时，谓语动词的形式要根据它们所代替的内容来定。如：
All who have studied this question have come to the same conclusion.
None is more qualified for the task than he.
3. 由连接词连接的名词或代词作主语
（1）由and或both ... and ...连接的并列主语，如果意义为复数，谓语动词通常用复数。但当and不表示并列意义，而是连接两个在意义上表示同一人、物、概念或由两个部件配成的物品时，谓语动词则用单数形式。如：
Both Mike and Jim have red hair.
The writer and reporter has given us a talk.
There is a watch and chain on the table.（watch and chain带链的表）
（2）当主语后跟有说明主语的修饰语，如由with, but, as well as, along with, rather than, together with, including, in addition to等引导的短语时，谓语动词的人称和数与主语保持一致。如：
The professor, together with his students, is dining here tonight.
（3）由or, either ... or ..., neither ... nor ..., not only ... but also ...等连接的名词或代词作主语时，谓语动词的人称和数要与邻近的主语相一致。如：
Either his brother or his friends are wrong.
Not only I but also my sister is fond of reading.
4. 从句及非谓语动词作主语
（1）名词性从句作主语时，谓语动词通常用单数。但如果是两个或两个以上的从句由and连接表示两个概念时，谓语动词用复数。另外，what从句作主语时，谓语动词的数由其表示的意义来决定。如：
Whether it is a good plan or not is a matter for argument.
What caused the snow slide and how many tourists were injured are still unknown.
What I wanted to find out first was how long it was going to take.
You need not get any more stamps. What we have are enough.
（2）动词-ing形式短语或不定式短语作主语时，谓语动词通常用单数。如：
Driving a car during the rush hour is tiring.
To master science means to master laws of nature.
高考链接
用be动词的适当形式填空。
1. While running regularly can’t make you live forever, the review says it ________ more effective at lengthening life than walking, cycling or swimming.
2. Fast food ________ full of fat and salt; by eating more fast food people will get more salt and fat than they need in their diet.
3. Leaving the less important things until tomorrow ________ often acceptable.
4. Confucius believed knives would remind people of killings and ________ too violent for use at the table.
5. Yangshuo ________ really beautiful. A study of travellers conducted by the website TripAdvisor names Yangshuo as one of the top 10 destinations in the world.
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