Question

No reptiles can fly. All birds can fly. Which of the following must be true?

• A. No birds are reptiles
• B. All reptiles can fly
• C. All flying creatures are birds
• D. Some birds are reptiles

Hint:

If Set A is completely inside Set B and Set B has no common elements with Set C, then Set A and Set C can never overlap.

Answer 1

The Correct Option is A

Concept: This is a syllogism problem based on set relationships. Let: \[ R = \text{Reptiles}, \quad F = \text{Flying creatures}, \quad B = \text{Birds} \] Given: \[ R \cap F = \emptyset \] (No reptiles can fly) and \[ B \subseteq F \] (All birds can fly) Since all birds belong to the set of flying creatures and no reptile belongs to the set of flying creatures, birds and reptiles cannot overlap. \[ B \cap R = \emptyset \] Therefore, \[ {\text{No birds are reptiles}} \] Hence, Option (A) is correct.