The children cleaned the bus yesterday.
过去式的否定:The children didn't clean the bus yesterday.
否定回答:No,they didn't.
肯定回答:Yes,they did.
一般疑问:Did the children clean the bus yesterday?
对yesterday提问:When did the children clean the bus?
The children cleaned the bus yesterday.
过去式的否定:The children didn't clean the bus yesterday.
否定回答:No,they didn't.
肯定回答:Yes,they did.
一般疑问:Did the children clean the bus yesterday?
对yesterday提问:When did the children clean the bus?