Number set — pick the odd number out (all others are composite): 4, 6, 8, 9, 10, 11, 12

Introduction / Context:
This is a property-based odd-one-out question. The simplest distinguishing feature among the listed integers is “prime vs. composite.” Identify the only prime to find the outlier.

Given Data / Assumptions:

• Numbers: 4, 6, 8, 9, 10, 11, 12
• Exactly one should be different by a basic number-theory property.

Concept / Approach:
Check primality. A prime has exactly two positive divisors (1 and itself). Composite numbers have more than two factors. Quickly factor each number to classify it.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer:
11