谓语动词后面接的是and连接的两个词,谓语动词单复数是根据哪个来定

and连接的两个词通常看成复数，其后谓语动词通常用复数。如：Tom and I are students.
如果两个词虽然由and连接，但如果只同一个人或物（成套的物），则谓语动词用第三人称单数形式。如：The writer and professor is going there. 那位作家兼教授要去那儿。

看完下面的讲解后，再看看家里语法书上的主谓一致部分，会理解得更好。
两个普通名词并列时冠词的使用
(1)如果两个名词代表两个人或事物，通常在各个名词前都要用冠词。
The teacher and the parent of the lad were discussing his case.
老师和这个年轻人的父亲正在谈论这件事。
I met a journalist and an author in the club.
我在俱乐部遇见了一位记者和一个作家。
A boy and a girl may not always agree on such a question.
一个女孩子和一个男孩子对于这个问题不可能总是有一致的意见。
He has bought an English and a French dictionary.
他买了一本英语词典和一本法语词典。
The first and the second chapter of our book are open to discussion.
欢迎大家讨论我们这本书的第一章和第二章。
Have you seen the red and the white roses in our garden?
你有没有在花园看到红玫瑰白玫瑰？(两种花)
Read the sixth and the last paragraphs of the text.
请朗读第一段和最后一段。 (指两段)
提醒：只要不引起歧义，也可以用一个冠词指两个人或事物。
The first and second chapters of our book are open to discussion.
欢迎大家讨论我们这本书的第一章和第二章。
A doctor and nurse are provided for them.
给他们提供了一个医生一个护士。
(2)如果指同一个人或事物，或指整体的一部分，一般只用一个冠词。
Have you a Chinese and English dictionary?
你有没有汉英词典？
Have you seen the red and white roses over there? (一种花，两种颜色)
Read the sixth and last paragraph of the text.
请朗读第六段，即最后一段。(指同一段)
(3)有些名词常成对出现被认为一体时，一般只用一个冠词。
Have you got a needle and thread here? I want to sew a button on.
你有没有针线啊？我想把扣子钉上。
By archery we mean shooting with a bow and arrow.
箭术指的是用弓和箭射击。
There is a knife and fork in the cupboard.
在碗柜里有一副刀叉。
类似的情况有a cup and saucer（茶杯托）， a horse and cart（马车），a coat and tie, a watch and chain, the King and Queen, etc
提醒：有时，即使是指同一个人或经常成对出现的人或物，如果强调每个对象，或想分别给以清晰的概念，也可重复冠词。
I bought a watch and a chain.
He has a father and a mother.
She is a journalist and an author.
Young Li has become a more matured and a wiser man.
The husband and the wife were discussing the education of their son.

need是个动词啊！动词是不存在单复数的，加s是因为主语是单数，单数的主语时，谓语动词要加s来变第三人称形式。动词本身是没有复数的。只有主语和宾语有复数。