同学,很高兴回答你的问题
正确答案：
This classroom is ours(改为一般疑问句）
Is this classroom yours?
Tony took my ball(改为否定句）
Tony didn't take my ball.
I finished my work yesterday.(改为否定句）
I didn't finish my work yesterday.
He felt happy.(改为一般疑问句,并用肯定回答）
Did he feel happy?
Yes,he did.
It was on the water.(改为一般疑问句,并用否定回答）
Was it on the water?
No,it wasn't.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
不明白请继续追问,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^