We'd better set off or it will be dark __________ we know it.
When the man came in, gun in hand ,we all stood there,______.
After winning the singing competition, she thought herself ___ in her neighborhood
--- I' m surprised to hear that Sue and Paul have ________ . ---So am I. They seemed very happy together when I last saw them.
As there is less and less coal and oil, scientists are exploring new ways of making use of______________ energy, such as sunlight, wind and water for power and fuel.
The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.