If the floods get worse we must(will have to)leave the house.he said.

　　他说：如果洪水涨得更高，我们只好离开这所房子。相当于：

　　He said that if the floods got worse they would have to leave the house.

　　他说如果洪水涨得更高，他们就得离开那所房子。

　　When it stops snowing we must start digging ourselves out，I sald.

　　我说：等雪一停，我们就得挖一条路出去。相当于：

　　I said that when it stoppd snowing we would have to start digging our- selves out.

　　我说等雪一停我们就得挖一条路出去。

　　We must mend the roof properly next year，he said.

　　他说：明年我们得把屋顶好好修理修理。相当于：

　　He said that they would have to mend the roof properly the following year.

　　他说下一年他们得把屋顶好好修理修理。

　　I have just received a letter，he said.I must go home.

　　我刚刚收到一封信，他说，我必须回家去。相当于：

　　He said that he had just received a letter and would have to go home.

　　他说他刚刚收到一封信，他得回家去。(如果他说话后立即回家了，则更常用had to，因为 had to的含义是他马上动身了。)

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