AMC10 2000 A

AMC10 2000 A · Q21

AMC10 2000 A · Q21. It mainly tests Logic puzzles.

If all alligators are ferocious creatures and some creepy crawlers are alligators, which statement(s) must be true? I. All alligators are creepy crawlers. II. Some ferocious creatures are creepy crawlers. III. Some alligators are not creepy crawlers.

如果所有短吻鳄都是凶猛的生物，并且一些诡异的爬行动物是短吻鳄，那么以下哪项（些）声明必须为真？I. 所有短吻鳄都是诡异的爬行动物。II. 一些凶猛的生物是诡异的爬行动物。III. 一些短吻鳄不是诡异的爬行动物。

(A) I only 仅I

(B) II only 仅II

(D) II and III only 仅II和III

(E) None must be true 无须为真

Answer

Correct choice: (B)

正确答案：（B）

Solution

Answer (B): From the conditions we can conclude that some creepy crawlers are ferocious (since some are alligators). Hence, there are some ferocious creatures that are creepy crawlers, and thus II must be true. The diagram below shows that the only conclusion that can be drawn is existence of an animal in the region with the dot. Thus, neither I nor III follows from the given conditions.

答案（B）：根据条件我们可以推断，一些“爬行怪物”是凶猛的（因为其中一些是短吻鳄）。因此，存在一些既凶猛又属于“爬行怪物”的生物，所以 II 必然为真。下图表明，唯一能得出的结论是在带有点的区域中存在一种动物。因此，I 和 III 都不能由给定条件推出。

Topics

LM.001 Logic puzzles