复数句50句 小学6年级水准 急用

1.this is my toothbrush (These are my toothbrushes.)
2.she is a woman doctor (They are women doctors.)
3.she runs a big business.(They run big businesses.)
4.Is there a watch on the desk? (are there some watches on the desk)
5.That is his friend. (Those are his friends.)
6.This is a hand （These are hands）
7.Is that yourbackpack? （Are those your backpacks?）
8.I am English teacher.（We are English teachers.）
9.What color is it? （What color are they? ）
10.Are you in Class One?（ Are you in Class One?）
11.Yes,I am.（Yes,we are.）
12.He wants to buy a bottle of orange juice（They want to buy some .bottles of orange juice.）
13.Here 's a map of China fou you （here are some maps of China for you）
14.It is a yellow leaf （They are yellow leaves.）
15.im free tomorrow （We will be free tomorrow.）

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？？ 什么是复数句