Which of the following letter-clusters will replace the question mark (?) in the given series?
XJPC YLOA ZNNY APMW ?

Let's trace the pattern for each position of the letter-clusters:
1st letter: X
+1

​
Y
+1

​
Z
+1

​
A
+1

​
B

2nd letter: J
+2

​
L
+2

​
N
+2

​
P
+2

​
R

3rd letter: P
−2

​
O
−1

​
N
−1

​
M
−2

​
… Wait, let's look closer at the positional values of the 3rd letters:

P=16

O=15

N=14

M=13

Following the −1 trend: 13−1=12→L? Let's check options. None have L as 3rd letter except BRLU. Let's re-verify:

Ah, look at the options: CRKU, BRLU, BRKU, BQKU. Let's re-examine 3rd letter: P(16)→O(15)→N(14)→M(13)→L(12). This matches BRLU.

4th letter: C(3)
−4

​
A(1)
−2

​
Y(25)
−2

​
W(23)… Let's look at the actual values:

C(3)
−4

​
A(27−4=23→W? No, the sequence given is C, A, Y, W.

C=3

A=1 (difference −2)

Y=25 (difference −2)

W=23 (difference −2)

Next letter: 23−2=21→U.

Thus, the next cluster is BRLU.