语法题,I suppose you are not serious,________?A.do I B.don't I C.are you D.aren't you这个什么情况下用don't ________,I should ask them some questions.A.Should they come to us B.If they come to usC.Were they come to us D.Had they come to usSome cities have passed laws that allow coal and oil_____only if their sulfur content is low.A.burning B.to burn C.being burned D.te be burnedallow sb to do 和allow sb dong 都可以的吧为什么不选其他的,请大家给我个详尽的解释哈,

D,B,D
都是根据句意
我估计你不是认真的，你是吗？
如果他们来了，我就该去问些问题。
allow sb. to do;allow doing;allow sth. to be done

1.C
主语是第一人称,主句谓语是think,believe,expect,suppose,imagine等引导的定语从句,疑问部分与宾语从句相对应构成反意疑问句.
I don't think he is bright,is he?
We believe she can do it better,can't she?
目前我没遇到过用don't 的
2.A,虚拟语气的省略形式,是对将来的虚拟,基本句型为：
If sb did sth/were to do sth/should do sth,sb should do sth.
前面部分只有那三种形式!自己去套
A 选项完整形式为If they should come to us,
3.可以确定只有allow sb to do的形式,没有allow sb doing,煤和石油是被烧,故选D