所有的名词性从句（主语从句、表语从句、宾语从句、同位语从句）都要考虑时态的问题,如：
It was true that they were true sisters.
The problem was that whom we could get to replace her.
I said that I was very unhappy.
It was a question how he had done it.
当从句为客观真理的时候,时态不变.
The teacher told us that the earth moves around the sun.
It was true that water freezes at thirty-two degrees Fahrenheit.
希望我能帮助你解疑释惑.