有一读者问：我在《科技英语学习》上看到这样一个句子：
(1)He usedn't /used not/didn't use to smoke fifty cigarettes a day, did he?
这里是否应将did he改作used he?
这里的附加疑问句既可用did he,亦可用used he。但据权威语法著作《英语语法大全》 （A Comprehensive Grammar of the English Language ）说，在附加疑问句中通常皆用助动词do，换言之，这里通常皆用did he。再如：
(2)He used to smoke, didn't he ?
(3)He usedn't to smoke, did he ?
顺便提一下，情态动词used to（也有人认为它更像是一个助动词）的否定式除上述句（1）所给的usedn't, used not和didn't use to之外，还有didn't used to,虽然有人认为它有点不够规范，实例如：
(4)— I hope he used to make more sense.
— He did. He didn't used to be at all like the way he is now.
(5)— You didn't used to feel like this.
— Oh, Dad, what's the use of talking like that?
