I don`t think he is a student,_is he____?
当主句的主语是I think/guess/suppose 等表思维的动词和I'm afraid 时.
尾句反问从句的主语和谓语,又由于don't 是否定的转移,是否定is 的,所以,用is he?
he dosen`t think she is a student,_does he____?
当主句的主语不是上述的情况时,反问主句的主语和谓语,所以用do he?