Classification – Odd one out (interval span) Each option denotes a closed interval [a, b]. In three options, the span b − a equals 2; in exactly one option, the span is different. Identify the interval with a different span.

Introduction / Context:
Intervals can be compared by their span (b − a). Test-makers often keep three spans equal and alter one to create a unique outlier. Identifying the inconsistent span is a quick arithmetic check.

Given Data / Assumptions:

• Intervals: 11–13, 12–14, 17–19, 18–22
• Interpretation: closed intervals [a, b] with integer endpoints

Concept / Approach:
Compute b − a for each interval. If three intervals have span 2 and one has a different span, that different one is the odd element. (We compare spans only; whether endpoints are prime is irrelevant here.)

Step-by-Step Solution:
11–13 → span = 13 − 11 = 2 → fits pattern.12–14 → span = 14 − 12 = 2 → fits pattern.17–19 → span = 19 − 17 = 2 → fits pattern.18–22 → span = 22 − 18 = 4 → breaks pattern.

Verification / Alternative check:
Even if you looked for prime twins, both 11–13 and 17–19 are twin-prime intervals; however, 12–14 includes composites. The span test alone consistently isolates one unique outlier (18–22), which is the intended basis.

Why Other Options Are Wrong:

• 11–13: Span 2.
• 12–14: Span 2.
• 17–19: Span 2.
• None of these: There is a single different span (18–22).

Common Pitfalls:
Mixing multiple criteria (e.g., primes and parity) and missing the simplest invariant—span equality.

Final Answer:
18-22