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。