—I’m afraid you missed a fantastic lecture yesterday. How come you were absent from it?—If you _______ know, I asked for a day off and visited a relative of mine in hospital.

Hurry up, or you ______ catch the train. 

--- I heard they went skating in the mountains last winter. --- It ______ true because there was little snow there.

In China when the traffic light is red, you ________ cross the road.

According to his will, his money ____be used to build a school instead of a market.