In the English alphabet, the first 4 letters are written in opposite order, and the next 4 letters are written in opposite order and so on; and at the end Y and Z are interchanged. Which will be the fourth letter to the right of the 13^th letter?

The correct answer is T.

Step 1: Understand the position of the target letter in the original sequence

We are asked to find the letter that is the 4^th letter to the right of the 13^th letter in the modified alphabet.

Moving 4 steps to the right from the 13^th position corresponds to the following position:

$13+4=17$

So, we need to find which letter occupies the 17^th position in the modified alphabetical order.

Step 2: Analyze the rearrangement rule

The English alphabet has 26 letters (A to Z).

The rule states that the letters are divided into blocks of 4 and reversed within each block, up to X (since 24 letters make 6 complete blocks of 4), and finally Y and Z are interchanged:

• Block 1 (Positions 1–4): A, B, C, D → reversed to D, C, B, A
• Block 2 (Positions 5–8): E, F, G, H → reversed to H, G, F, E
• Block 3 (Positions 9–12): I, J, K, L → reversed to L, K, J, I
• Block 4 (Positions 13–16): M, N, O, P → reversed to P, O, N, M
• Block 5 (Positions 17–20): Q, R, S, T → reversed to T, S, R, Q
• Block 6 (Positions 21–24): U, V, W, X → reversed to X, W, V, U
• End (Positions 25–26): Y, Z → interchanged to Z, Y

Step 3: Determine the letter at the 17^th position

The 17^th position falls as the first letter of Block 5 (which covers positions 17 to 20).

The original letters in Block 5 are Q (17^th), R (18^th), S (19^th), and T (20^th).

When this block of 4 letters is written in reverse order, it becomes: T, S, R, Q.

Thus, the letter at the 17^th position is T.