所有的名詞性從句（主語(yǔ)從句、表語(yǔ)從句、賓語(yǔ)從句、同位語(yǔ)從句）都要考慮時(shí)態(tài)的問題,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.
當(dāng)從句為客觀真理的時(shí)候,時(shí)態(tài)不變.
The teacher told us that the earth moves around the sun.
It was true that water freezes at thirty-two degrees Fahrenheit.
希望我能幫助你解疑釋惑.對(duì)，狀語(yǔ)從句中則存在“主將從現(xiàn)”的情況，如：If it doesn't rain tomorrow, I will do some shopping.When winter comes, the birds will fly to the south.if和when分別引導(dǎo)條件和時(shí)間狀語(yǔ)從句，這種情況下存在“主將從現(xiàn)”的情況。希望我能幫助你解疑釋惑。