I suppose he'serious,don't I 句子哪错了?

I suppose he'serious,don't I 句子哪错了?
I suppose he'serious,don't I 句子哪错了?

I suppose he'serious,don't I 句子哪错了?
isn't he?

isn't he?

don't I ->isn't he?
http://www.265ks.com/englishlearning/chyf/200603/95148.html