-- _____is that used for?---_____ the floor.
After staying in hospital for long, the patient was advised to go to the seaside to __________ his health.
I was walking down the street, when I suddenly saw a car __________ a huge pine.
I soon found that the work I was doing had already been done by someone else —__________ I was wasting time.
__________ with foreign countries can bring us much information about the world.
—Have you known Dr. Jackson for a long time?—Yes, since she________ the Chinese Society.