must/ had to
如果直接引语中的情态动词没有过去时的形式(例:ought to， had better, used to，must, need)和已经是过去时的形式时，(例:could, should, would, might)不再变。
that day 那天
that night 那天晚上
this week 本周
that week 上周
the day before前一天
the day before yesterday 前天
two days before 前两天
three days ago三天以前
three days before 前三天
last week 上周
the week before前一周
the next day /the following day第二天
next week 下周
the next week 第二个星期
the following month第二个月
She said, "Our bus will arrive in five minutes."
→She said that their bus would arrive in five minutes.
He said, "Can you swim, John?"
→He asked John if he could swim.
"You have finished the homework, haven't you?" my mother asked.
→My mother asked me whether I had finished the homework.
"Do you go to school by bus or by bike?"
→He asked me if I went to school by bus or by bike.
She asked me, "When do they have their dinner?"
→ She asked me when they had their dinner.
④直接引语如果是祈使句，间接引语应改为"tell (ask) sb (not) to do sth."句型。
"Don't make any noise," she said to the children.
→She told (ordered) the children not to make any noise.
"Bring me a cup of tea, please," said she.
→She asked him to bring her a cup of tea.
He said, "Let's go to the film."
→He suggested going to the film.
或He suggested that they should go to see the film.
⑥直接引语是感叹句时，间接引语为what 或how 引导，也可以用that 引导。
She said, "What a lovely day it is !"
→She said what a lovely day it was .或She said that it was a lovely day.
He said to me, "I have taught English since he came here ."
→He told me that he had taught English since he came here.
eg: "I have bought an expensive car , " said the boss.→The boss said he had bought an expensive car.
eg: I often tell him , "You are the luckiest boy I have ever seen . " → I often tell him he is the luckiest boy I have ever seen . "
He said, "I get up at six every morning。" →He said he gets up at six every morning。
Light travels faster than sound.光速比声速快。
The earth goes around the sun.地球绕着太阳转。
The moon goes around the earth.月球绕着地球转。