谓语受主语支配，它必须在人称和数等方面与谓语保持一致。
I 语法形式上一致
(1)单数的名词、代词、动词不定式、动名词短语或从从句作主语时，谓语动词用单数。
What I hate most is telling lies.
To become a doctor is his ambition.
Whether she comes or not is of no matter·
[注]“what”引导的从句作主语，如果它后面的表语是复数形式，谓语动词亦可以用复数。
What I said is right.
What we need badly here are doctors.
(2)由"and"连接并列主语时：
1)一般情况下谓语用复数。
What she says and what she does don’t agree·
Swimming in the summer and skating in the winter are my hobbies
In the city are to be found both the most renowned scholar and the scoundrels(无赖)
2)并列的主语如果表示同一个人、同一事物或同一概念时，谓语动词用单数形式，而且“and”后面的名词前没有冠词或物主代词修饰。
My house and home is at 1707 Maryland drive.
Bread and butter is daily food for breakfast.
Her best friend and adviser has changed her idea again.
The Air-Marshal and Chief-of-Staff was killed in the air crash.
表示同一概念的类似短语有：
a block and tackle(滑轮组);the needle and thread(针线);brandy and soda(掺苏列日兰地);sale and water(盐水);law and order(法律秩序);a cup and saucer(茶杯碟子); the ebb and flow (盛衰; 涨落); the rope and pulley (滑轮绳索)
watch and chain(有表链的手表);soap and water(肥皂水);etc。
There is my watch and chain on the dressing-table.
[注]若“and”后面的名词前有冠词或物主代词修饰，谓语动词用复数形似。
The bread and the butter are on sale.
My watch and my pen were stolen yesterday.
My friend and the classmate Jane are in the classroom.
3) 由“and”连接的并列单数主语前有“each, every, no , many a ”等修饰时，谓语动词用单数形式。
Many a boy and many a girl in the class has seen this film.
No teacher and no student is present.
Every man, woman, and child in this community is aware of the terrible consequences of the habit of smoking.
[注]复数主语后面加上"each"，谓语用复数。
The girls each have their own mothers.
The old worker and the young each have their own tools.
4)"and"后面加上"not"，谓语用单数。
The farmer and not the city dweller is hurt when food prices fall.
Mr.Brown，and not I，is chosen to be the representative of the company.
It is conflict and not unquestioning agreement that keeps freedom alive.
5)注意在某些成语里的主谓一致：
Time and tide wait for no man.(岁月不留人。)
Truth and honesty is the best policy.(诚实为上策。)
