【问】 Our visitors should have arrived at the airport by now.

现在他们本应该到达机场的。

上面的译文是否正确?

【答】 在没有上下文的条件下，should+完成时不定式的最常见用法，就是表达“本应该做而实际上没有做某事”(If you say that something should have happened，you mean that it did nothappen，but you expected it to happen or you wish that it had happened.)例如：

1. You should have thought about that before you invited her. (EED)

在你邀请她之前本应该想到这一点的。

2. You should have washed the wound. (But you haven't.)(Wells)

你本应把伤口洗一洗。(但你却没有洗。)

但是，你提出的句子，由于受by now的制约，具有另外的含义。在这里，助动词should表示“推测”、“估计”(If you say that something should have happened by now，you mean that ithas probably happened by now)。例如：

1. Have you heard from Maria? She should have started her job on Monday. (CGEL)

你收到玛丽娅的信了吗?她也许在星期一就开始工作了。

2. Dear Mom，you should have heard by now that I'm O.K..

亲爱的妈妈，你可能已经听说我一切都好。

按照后一种理解，你提出的句子似应译为：我们的客人此刻应该到达机场了。

(参见上条)