语法题,

问题描述:

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 us
C.Were they come to us D.Had they come to us
Some 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 burned
allow 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,

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