case是单子、案例的意思，例如：
1.It was yet another case where the human eye outperformed radar.这是肉眼胜过雷达的又一事例。
2.More than 80% of those cases can be attributed to contact with contaminated water and a lack of proper sanitation.而其中超过80%的事例可以归结于接触污染水和缺乏卫生条件。
3.Could you give us a concrete case?你能不能给我们举个具体事例？。
