Question

I think this T-shirt is perfect.的反意问句是……?

Answer 1

I think this T-shirt is perfect, isn't it?

复合句的反意疑问句,其助动词要与表达主要思想的从句的谓语动词一致.例如：

Tom told me that you were going to America, weren't you?

汤姆告诉我你要去美国,是吗?

因此这里反意疑问句的助动词要用isn't it?（this T-shirt is perfect为其主要思想的从句）而不是don't I?