Alphabet Pattern — “PERPENDICULAR, ERPENDICULA, RPENDICUL, ?”. Observe the trimming pattern and supply the next inner substring.

Introduction / Context:
Many alphabet/pattern problems progressively trim characters from a word’s ends, revealing nested inner substrings. Here the word evolves: “PERPENDICULAR” → “ERPENDICULA” → “RPENDICUL” → ? We must infer the consistent trimming rule and predict the next term.

Given Data / Assumptions:

• Term1: PERPENDICULAR.
• Term2: ERPENDICULA (removed the first and last letters).
• Term3: RPENDICUL (removed first and last again from Term2).

Concept / Approach:
The visible rule is: at each step, drop the first and the last character, yielding the inner substring. Applying this once more to Term3 should produce the next inner string.

Step-by-Step Solution:

Verification / Alternative check:
Check lengths: 13 → 11 → 9 → 7 (consistent −2 each step). “PENDICU” has 7 characters, which fits the expected sequence length.

Why Other Options Are Wrong:

Common Pitfalls:
Overlooking that each new term is derived from the previous term (not directly from the original) and that both ends are trimmed simultaneously.

Final Answer:
PENDICU