【问】 (A) They must have arrived by now.

现在他们想必已经到达。(张道真：《实用英语语法》，1995年修订重印本，外研社，P.253)

(B) They ought to have arrived by now.

现在他们想必已经到达。

must have arrived 与 ought to have arrived在表“推测”时，意思是不是相同?

【答】 在上面的句子里，must have arrived与ought to have arrived都是推测“(他们)已经到达”，但是说话人对其陈述的肯定性程度却有很大区别。must have arrived表明说话人对自己所描述事件确信无疑，也就是说，说话人完全肯定其说法的正确性。而ought to have arrived则表明说话人对自己所描述的事件仅仅是个猜测而已，也就是说，说话人并不能完全肯定其说法的正确性。在翻译时，应把它们之间的区别表达出来：将must have done译为：“一定”、“必定”、“肯定……”、“必然”、“准是……”;而将ought to have done译为“可能……”、“或许……”、“也许……”、“想必……”、“该……”：

1.“The lights have gone out.”

“A fuse must have blown. ”(AED)

“灯灭了。”

“一定是保险丝烧断了。”

2. If he had started at nine o’clock，he ought to have been in London by eleven o’clock.(Palmer)

如果他是九点钟出发的话，那他十一点钟该到达伦敦了。