Have you ever been to Mount Huangshan, ___________is famous for its pine forests and "sea of clouds"?
The news _____ the football team won the game made us happy.
Come and see me whenever _____.
He is made ______ monitor of our class.
Long ago, man used to ______ with his hands but now man is used to ______ with machines, and sometimes a robot is used to ___ instead of people.
There is no need ______ because Mr. Smith is still sleeping.