BBC news 2010-11-02 加文本

1. and clearly that was vital because if these devices had got through the initial security screening, and so without that tip-off, they may well have exploded.

虚拟语气

与过去事实相反的虚拟：

If + had done + ..., ... would (might) have done ...

If I had known your telephone number yesterday, I would have phoned you.

 (I didn't know your telephone number.)

If you had come here a littleearlier just now, you might have met her.

 (You didn't come here earlier.)

2.Police in Northern Ireland say a bomb discovered in a car at Belfast International Airport at the weekend could have been there since last year.

这句话的主语和谓语是：Police in Northern Ireland say，后面是宾语从句。宾语从句的主干是：a bomb could have been。could have been表示猜测。