it is said that的问题

it is said that的问题 It is said that…时态问题, It is said that. it is said that it is said that用法 It is sometimes said that... 关于it is said that It is said that the it is said that dogs. it is said that的固定结构可以改成 it was said that? 为什么是It is said that 而不是It said that It is said that that was all that he said.