The class was held hostage by a hooded gunman.
全班学生被一名蒙面持枪歹徒挟为人质。
2.reckon 认为
Some people reckon that space exploration is a sheer waste of time and money while a majority of other people believe that it is of great importance.
有些人认为太空探索纯属浪费时间和金钱，但是大多数人认为太空探索有着非常重要的意义。
3.bounce off 弹开，反弹
Short sound waves bounce off even small objects.
短声波即使遇到小物体都会产生回音。
4.upshot 结果，结局
The upshot could be a much bigger bubble in the future.
结果可能是日后出现更大的泡沫。
