---I called you last night, but nobody answered.---Oh, I usually___off my cellphone by 9:00 p.m.
20. In many places in China, ____ bicycle is still _____ popular means of transportation.
19. My grandpa has many hobbies which _________ from collecting stamps to planting flowers.
18. It was ______ back home after the experiment.
17. -- My mother always tells me to try my best _______ many difficulties. -- I can’t agree any more. _______ you put your heart into work, you can overcome them.
16. Charles Babbage is generally considered _______ the first computer.