UPSC CSE Prelims 2026

The correct option is D - P, Q and R.

Why this is correct

This is a LOGICAL REASONING question based on Syllogisms. We can analyze the logical flow of the statements using the transitive property (If A is B, and B is C, then A is C):
1. Every red is blue (Red ⊂ Blue)
2. Every blue is green (Blue ⊂ Green)
3. Every green is yellow (Green ⊂ Yellow)

By combining these statements, we get a nested hierarchy: Red ⊂ Blue ⊂ Green ⊂ Yellow.

Now, let's evaluate the conclusions:
P. Every blue is yellow: Since Blue ⊂ Green and Green ⊂ Yellow, it logically follows that Blue ⊂ Yellow. This is correct.
Q. Every red is green: Since Red ⊂ Blue and Blue ⊂ Green, it logically follows that Red ⊂ Green. This is correct.
R. Every red is yellow: Since Red ⊂ Blue, Blue ⊂ Green, and Green ⊂ Yellow, the entire set of Red is contained within the set of Yellow. This is correct.

Why the other options are incorrect

• Option (a) - P and Q only: This option is incorrect because it excludes statement R, which is a valid logical deduction from the given premises.
• Option (b) - Q and R only: This option is incorrect because it excludes statement P, which is a direct consequence of the relationship between Blue, Green, and Yellow.
• Option (c) - P and R only: This option is incorrect because it excludes statement Q, which is a valid deduction based on the relationship between Red, Blue, and Green.

Key Concept

The transitive property of categorical syllogisms, where if set A is a subset of B and B is a subset of C, then A is necessarily a subset of C.