[求助]逻辑题一

oddyuibe

Consumer income reports produced by the government distinguish between housholds and families by means of the following definition:" A family is a houshold containing a householder and at least one person related to the householder."Except for the homeless and people in group living quauters, most people live in households.

According to the definition above, which of the following must be true?

a) All householders are members of families
b) All families include a house holder

The given answer is B.
A为什么不可以呢？请指教
[em10]

oddyuibe

To Peace

oh, I see.

多谢你的指点，这有一点像形式逻辑呀~

Peace

根据题干：familiy 的必要条件有两个：

1 contain a household   2 at least one person related to the householder.

所以familly 成立则 条件1成立 ==》 B must be true.
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同理，假设有一个householder， 而没有 a person related to him，那么光这一个householder就组不成家庭，也r就不能称其为家庭成员了。
==》A 不一定 true