(2012·南京高二检测) Some people are worrying about the possibility _______ mobile phones could be responsible for a range of illnesses, from rashes (皮疹) to brain tumors.
The police say there is a $50,000 _______ for any information that helps them find the killer.
Most whales must come up for air after several minutes, _______ a few can stay under water for an hour or more.
The numbers that researchers get from the experiments can be _______, just like number puzzles.
_______ the house is empty, memories flood my mind of a time when it was filled with life.
By the time a child is five, he _______ hundreds of hours of television.