1、在回答 must 开头的一般疑问句时,肯定回答用 must,否定回答用 neednt或 dont have to. 如:1)Must I finish my homework before eight oclock?Yes, you must.2)Must I attend the meeting?No, you neednt(No, you dont have to). You can ask Tom to go instead.2、在回答 may 开头的一般疑问句时,肯定回答用 may,否定回答用 mustnt. 如:1)May I watch TV after supper?Yes, you may. / No, you mustnt.2)May I stop here?No, you mustnt.3、在回答 need 开头的一般疑问句时,肯定回答用 must,否定回答用 neednt. 如:1)Need we stay behind after school?Yes, you must.2) Need he go now?No, he neednt.