Was she a teacher many years ago? There weren‘t any trees before? Did she teach English five years ago? 改一般疑问句很简单,有be动词的话只要把be动词(be动词一般为:is,are,was were.)提前就好了.如果没有be动词的话就自己加助动词(助动词为:do ,did ,does)加在句首,如果是过去式记得did后面加原型,不要忘了变.一般的考点都是在这里. 改否定句的话就更简单了,只要在be动词或助动词后面加not或n't(not和n't没有区别,用哪个看你的习惯)就行了.