Question

改错： You should are sleeping. Her brother would likes it. They are going to buy a pair of shoe.

He's doing him homework.

Answer 1

You should 【sleep】should是情态动词，后面用动词原形
Her brother would 【like】 it would是情态动词，后面用动词原形
They are going to buy a pair of 【shoes】.a pair of是一双，用复数
He's doing 【his】 homework.他的作业，应该用物主代词his
有不会的可以再问我

Answer 2

You should are（be） sleeping.
Her brother would likes（like） it.（should ，would，could，can，will，may，might后加动词原形或be动词原形）
They are going to buy a pair of shoe（shoes）.(shoe鞋子是一双a pair of）
He's doing him（his） homework.（him 他，宾格 his他的，形容词性）

Answer 3

You should sleep.
Her brother would like it.
They are going to buy a pair of shoes.
He's doing his homework.

Answer 4

You should be sleeping.

Her brother would like it.

They are going to buy a pair of shoes.