单数句变复数句, 只要注意下面的六要素，问题便迎刃而解：
1．人称代词主格单数变成相应的人称代词主格复数，即I→we;you→you;she,he,it→they。 如：
She is a girl.→ They are girls.
2． am, is 变为 are。 如：
I'm a student. →We are students.
3．不定冠词 a, an 要去掉。如：
He is a boy. → They are boys.
4．普通单数名词要变为复数形式。如：
It is a cat. →They are cats.
5．指示代词 this, that 变为 these, those。如：
This is a book.→ These are books.
6． man, woman 作定语修饰可数名词时，要在 "数"上与被修饰名词保持一致。但其他名词修饰名词表示 "性质"时，不作变化。如：
He is a man doctor.→They are men doctors.
This is an apple tree.→They are apple trees.
※记住单数句变复数句的口诀。
单数句子变复数，变化规则要记住。
名词代词要变化，am, is 要变are。
this, that 该咋办，these, those 替代它。
he, she, it 要变啥，全部变 they 就行了。
I要变 we 别落下，名词后面把 s/es加。
名前冠词去掉它，其余成分原样加。
练习如下：
This is a man teacher.
2.He eats a tomato every day .
3.That is my sister .
4.It is a photo of her family.
5.She wants to see a movie .
6 IS this you aunt? -Yes,it is./NO,it isn't. This isn't my aunt.
7 It is a book. Is it a book? It isn't a book.
8 He is my father。 Is he your father?-Yes,he is./No he isn't. He isn't my father.
9 This dictionary is on the desk. Is this dictionary on the desk? This dictionary isn't on the desk.
10 This girl is my sister. Is this girl sister? This girl isn't my sister.
1, I have a car. we have cars.
2, He is an American boy. They are American boys.
3, It is a car. They are cars.
4, This is an eraser. These are erasers.
5, That is a backpsck. Those are backpacks.
6,I'm an English teather. We are English teathers.
7,It's a new shirt They are new shirts
8,He's a boy . They are boys.
9,She's a singer . They are singers.
10,What's this in English? What are these in English?