2000 AMC 10 Problem 21
Problem 21 of 25HarderCounting & Probability
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.
Answer choices
Show solution
Solution
Some creepy crawlers are alligators, and all alligators are ferocious, so those creatures are both creepy crawlers and ferocious. Hence some ferocious creatures are creepy crawlers, making II true.
Statement I fails because not every alligator need be a creepy crawler, and III fails because it is possible that all alligators are creepy crawlers. Only II must hold.
Thus, the correct answer is B.