Explanation:

- Let’s decode the pattern:

- 2 Zs, 3 Ys, 4 Xs, 5 Ws …

- The nth letter from the end repeats (n+1) times.

- The sequence goes from Z to A, each getting one more repeat than before.

- To find the middle term, count the total terms:

- Sequence starts at Z (position 26), continues down to A (position 1).

- Total terms = 2 (Z) + 3 (Y) + 4 (X) + ... + 27 (A)

- This is a series: 2 + 3 + ... + 27

- Total terms = (2 + 27) × 26 / 2 = 29 × 13 = 377

- The middle term is at position 189 (since 377/2 = 188.5, so 189th term).

- Now, sum the counts till reaching 189 to know which letter it is:

- Z: 2 terms (1-2)

- Y: 3 terms (3-5)

- X: 4 terms (6-9)

- W: 5 terms (10-14)

- ...

- The general count for nth letter: Number of terms till nth letter from last (Z is 1st from end) is:

S = sum_{k=2}^{n} k = (n(n+1)/2) - 1

- Let's find n where cumulative becomes >= 189.

- Try n = 18:

S = 18 × 19 / 2 - 1 = 171 - 1 = 170

- Next, n = 19:

S = 19 × 20 / 2 - 1 = 190 - 1 = 189

- So, the 189th term is at the completion of the 19th letter from end, i.e., on letter "I".

- Options:

1. H

2. I

3. J

4. M

- Correct answer is option: 2 - I