Adjacent-pair swapping in a word: If you swap (1↔2), (3↔4), (5↔6), … in “COMMUNICATIONS”, which letter becomes the 10th from the right in the new arrangement?

Introduction / Context:
Swapping adjacent pairs is a frequent test of string manipulation and indexing under time pressure. After performing the swaps, you must locate a letter by relative position (“10th from the right”) rather than by index from the left, which increases the likelihood of off-by-one mistakes.

Given Data / Assumptions:

• Word: COMMUNICATIONS (14 letters): C O M M U N I C A T I O N S.
• Operation: swap (1↔2), (3↔4), (5↔6), (7↔8), (9↔10), (11↔12), (13↔14).
• Query: identify the 10th letter from the right after swapping.

Concept / Approach:
Execute pairwise swaps carefully, then convert the “10th from right” into a left index: for a 14-letter string, the 10th from the right is position 14 − 10 + 1 = 5 from the left.

Step-by-Step Solution:

Verification / Alternative check:
Count from the right explicitly: N(1), S(2), I(3), O(4), A(5), T(6), I(7), C(8), U(9), N(10). The 10th from right is N, confirming the earlier index conversion.

Why Other Options Are Wrong:

• U / A / T match nearby positions but not the exact index (off-by-one traps).
• None of these: Not applicable because N is correct.

Common Pitfalls:
Miscounting from the right; forgetting to convert right-based indexing to left-based index correctly for even-length strings.

Final Answer:
N