2、
宾语从句与主句时态的一致。
1)主句是现在(或将来)时态时,宾语从句可根据实际需要用不同的时态。
如:He says Mary is playing with the cat .
He says Mary
often plays with the cat.
He says Mary
will play with the cat.
I think he left yesterday morning.
2) 主句时态是一般过去时,从句要用过去时态的某种形式。
He said Mary was playing with the cat.
He said he hoped to be back soon..
3)
当从句所表示的是客观事实或客观真理时,该从句都用一般现在时,不用过去时。
如:He said light travels much faster than sound.