We must study English hard or we can’t be in the library,(反义

We must study English hard or we can't be in the library,(反义疑问句）
说明原因,为什么反义哪个词
Open the windows,(反义疑问句）

答案应该是can we?
如果单纯是出现了must,那么这个题目应该用needn't we?
详细用法参考下面
must 的三种反义疑问句
既然多数人感到麻烦我就来讲一讲must反义疑问句的用法.
你记住,must反义疑问句就三种可能：
①must
②needn't
③变换句式
下面来讲一讲他们分别的用法,一般考试就这三种可能!
1、mustn't→must
mustn't在陈述句中的意思一般是不允许,禁止,所以他的反义疑问句用must或may
例：You mustn't smoke here,must you?或may you?
2、必须→needn't
当must在陈述句中作“必须”解时,它的反义疑问句就变成needn't
例：You must go now ,needn't you?
3、变换句式
在must表示推测,做“一定,准是”,简单的说就是must用于虚拟语气时
像数学一样我们引入一个“常量”——I am sure that
下面就能你那句话作为例子,我们变换一下.
He must have come yesterday.变换句式作
I am sure that he came yesterday.好我们应该分清,反义疑问句问的应该是I am sure that 后面的从句
所以,按照一般反义疑问句的规则得出结果
I am sure that he came yesterday,didn't he?
最后再把句子还原
He must have come yesterday,didn't he?
关键就在于这个题目强调的是or后面的部分,所以用can we?
Open the window,wouldn't/couldn't you?
因为你是祈求的语气,祈使句啊,要用那两个