I could sing this song three years agoI could not sing this song three years agowhen could you sing this song?He studied hard last yearHe studied not hard last yearHow did he study last yearJim was of...一般疑问句？Could you sing this song three years ago? Yes ，I could No ，I couldn't

Did he study hard last year? yes ，he did No ，he didn‘t

Was Jim often last for school last month? yes，he was No ，he wasn’t

Did she take any picture in the park last week? yes ，she did no ,she didn't