Q3: If a committee of 3 people is to be selected from among 5 married couples so that the committee does not include two people who are married to each other, how many such committees are possible? A. 20 B. 40 C. 50 D. 80 E. 120 这一题我选了20，但是错的。我对这一类型的题总是迷糊，不知道该拿他怎麽办。哪一位可以在这一类方面给我讲解讲解，可以让我更清楚一些。我又阅读过一些关于permutation and combination 的解释,但是我觉得没有多大用在做这类题时。不知道那位可以指点我一下。万分感激！！！ | 
