It was 80 years before Christopher Columbus crossed the Atlantic _____ Zheng He had sailed to East Africa.
_______ information cost him many chances of finding jobs.
How many more decades will have to pass ____ scientists succeed in providing a cure for cancer?
--- Where will you start your work after graduation? --- Mmm, it’s not been decided yet.I _______ continue my study for a higher degree.
Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production.
--- Where are you, Nancy? --- Here in the sitting room, _______ to Professor Smith.