Standing on the top of the hill, one would not do anything, but _____ the flowing of the clouds around me. 

Only when the war was over ____ return to his hometowns. 

John opened the door. There _______ he had never seen before.

So sudden an attack ________ that the enemy could hardly have any time to fly for their lives.

—Jack is always complaining about not having any money． —The problem is that he doesn't work hard and never ____．