--Mum, have you seen my U-Disk?--____________ you bought last Sunday? I'm afraid I haven't seen ________.
— It was cloudy yesterday. —_________ today.
It is reported that the United States uses ________ energy as the whole of Europe.
It was along the Mississippi River _________ Mark Twain spent much of his childhood.
At the meeting place of the Yangtze River and the Jialing River __________, one of the ten largest cities in the world.
Some insects __________ the color of their surroundings to protect themselves.