it would be possible.改否定（内详）It would be possible to have an observatory in our shcool.（改为否定句）_____ _____ _____ _____to have an observatory in our shcool.可不可以改成It wouldn't be possible to have an observatory in our shcool.把possible 改成impossible是答案，那么我这个改句算错么？would改成wouldn't有问题么？

It would be impossible to have an observatory in our shcool.或It wouldn't be possible to have an observatory in our shcool.

也可以用it would be impossible to-------

It would be impossible to have an observatory in our shcool.
impossible 是possible的反义词
这个句子考的应该就是possible的反义词,要明白出题人的意图~而且It would be ..时刻特定句式,有推测的意思,如果用It wouldn't be ..就太牵强了,语义和原来有了很大的变化~

字面上是可以的
would否定式后面加not 缩写wouldn't
但是一般英语习惯是把
possible改称impossible
更符合英语用法！