英语 反意疑问句 问题, I don✀t think he is bright,is he?

为您解答
我们一句一句来。
一，当使用I think/i don't think时，反义疑问句部分根据从句的肯否来决定。i don't think表达的其实是从句的否定，所以，反义疑问部分需要肯定。因此，你第一句是对的。
如：
①I don't think that you can do it, can you? (不用do I?)
②We don't believe that the news is true, is it? (不用do we?)

二，当是别人think时，我们反义疑问的是主句的部分，问那个主语是不是这么想的或做的，所以要根据主句的肯否，你第二句的didn't he里的he指的不是Mr.Smith，而是主语He。
如：
①They all think that English is very important, don’t they? (不用isn't it?)
②He didn't think that the news was true, did he?

I don't think he is bright,is he? He said Mr Smith was not going to attend the meeting,didn't he? 第一句是对从句否定，是因为主语是第一人称且动词是think.所以特殊。其它是对主句否定。