he bought a computer yesterday.变否定句

he bought a computer yesterday.变否定句 He bought a computer yesterday.(改为否定句) My brother bought some CDs yesterday怎样变否定句 he bought a pair of glasses yesterday.改成否定句和一般疑问句 They bought a good computer yesterday.（改为同义句） they have bought a computer 改成否定句 I bought a bike yesterday 怎么变同义句 I played a computer game yesterday afternoon否定句 he did his homework after school yesterday.变否定句 he bought a dictionary for himself怎么改否定句 He bought a storybook last month.(改为否定句） he bought a new bike last week (改为否定句)