there is no doubt that.和 it is no doubt that...的区别

there is no doubt that.和 it is no doubt that...的区别
为什么有的句子要用there is no doubt that.而有的句子又要用it is no doubt that...当然他们都是“毫无疑问”的意思,可用法上有什么区别呢?
这是一道改错题：there is no doubt that he passsd the exam.答案是将there改为it,为什么呢。