主谓一致 主谓一致
主谓一致是指：
1） 语法形式上要一致，即单复数形式与谓语要一致。
2） 意义上要一致，即主语意义上的单复数要与谓语的单复数形式一致。
3） 就近原则，即谓语动词的单复形式取决于最靠近它的词语，
一般来说，不可数名词用动词单数，可数名词复数用动词复数。
There is much water in the thermos.
但当不可数名词前有表示数量的复数名词时，谓语动词用复数形式。
e.g. Ten thousand tons of coal were produced last year.
Large quantities of water are needed.
In western countries, mountains of rubbish are thrown away each day.
1 并列结构作主语时谓语用复数
Reading and writing are very important.
注意： 当主语由and连结时，如果它表示一个单一的概念，即指同一人或同一物时，谓语动词用单数，and 此时连接的两个词前只有一个冠词。
The iron and steel industry is very important to our life.
典型例题
The League secretary and monitor ___ asked to make a speech at the meeting.
A. is B. was C. are D. were
答案B. 注： 先从时态上考虑。这是过去发生的事情应用过去时，先排除A.，C.。本题易误选D，因为The League secretary and monitor 好像是两个人，但仔细辨别， monitor 前没有the，在英语中，当一人兼数职时只在第一个职务前加定冠词。后面的职务用and 相连。这样本题主语为一个人，所以应选B。
2 主谓一致中的就近原则
1) 当there be 句型的主语是一系列事物时，谓语应与最邻近的主语保持一致。
There is a pen, a knife and several books on the desk..
There are twenty boy-students and twenty-three girl-students in the class.
2）当either… or… 与neither… nor， 连接两个主语时，谓语动词与最邻近的主语保持一致。 如果句子是由here, there引导，而主语又不止一个时，谓语通常也和最邻近的主语一致。 Either you or she is to go.
Here is a pen, a few envelopes and some paper for you.
3 谓语动词与前面的主语一致
当主语后面跟有with, together with, like, except, but, no less than, as well as 等词引起的短语时，谓语动词与前面的主语一致。
The teacher together with some students is visiting the factory.
He as well as I wants to go boating.
4 谓语需用单数
1） 代词each和由every, some, no, any等构成的复合代词作主语，或主语中含有each, every, 谓语需用单数。
Each of us has a tape-recorder.
There is something wrong with my watch.
2） 当主语是一本书或一条格言时，谓语动词常用单数。
The Arabian Night is a book known to lovers of English.
《天方夜谭》是英语爱好者熟悉的一本好书。
3） 表示金钱，时间，价格或度量衡的复合名词作主语 时，通常把这些名词看作一个整体，谓语一般用单数。(用复数也可，意思不变）。
Three weeks was allowed for making the necessary preparations.
Ten yuan is enough.
5 指代意义决定谓语的单复数
1） 在代词what, which, who, none, some, any, more, most, all等词的单复数由其指代的词的单复数决定。
All is right. (一切顺利。)
All are present. (所有人都到齐了。)
2） 集体名词作主语时，谓语的数要根据主语的意思来决定。如family, audience, crew, crowd, class, company, committee等词后用复数形式时，意为这个集体中的各个成员，用单数时表示该个集体。
His family isn't very large. 他家不是一个大家庭。
His family are music lovers. 他的家人都是音乐爱好者。
但集合名词people, police, cattle, poultry等在任何情况下都用复数形式。
Are there any police around?
3）有些名词，如variety, number, population, proportion, majority 等有时看作单数，有时看作复数。
A number of +名词复数+复数动词。
The number of +名词复数+单数动词。
A number of books have lent out.
The majority of the students like English.
population的谓语动词形式与表语一致，一般来说与分数，百分数连用时，谓语动词用复数。
6 与后接名词或代词保持一致
1） 用half of, part of, most of, a portion of 等词引起主语时，动词通常与of后面的名词，代词保持一致。
Most of his money is spent on books.
Most of the students are taking an active part in sports.
2） 在一些短语，如 many a 或 more than one 所修饰的词作主语时，谓语动词多用单数形式。但由more than… of 作主语时，动词应与其后的名词或代词保持一致。
Many a person has read the novel. 许多人都读过这本书。
More than 60 percent of the students are from the city.百分之六十多的学生都来自这个城市
参考资料：http://baike.baidu.com/view/84523.htm