Select the letter-cluster from among the given options that can replace the question mark (?) in the following series:
RBEH, RGOW, RLYL, RQIA, ?

The correct option is RVSP.

To find the missing letter-cluster that replaces the question mark (?), let us analyze the pattern followed by each letter position across the given series: RBEH, RGOW, RLYL, RQIA, ?

First letter position:
The first letter in every cluster remains constant:
R ⇒ R ⇒ R ⇒ R ⇒ R

Second letter position:
Let us look at the positional values of the second letters in the alphabet (A = 1, B = 2, ..., Z = 26):
B (2) + 5 = G (7)
G (7) + 5 = L (12)
L (12) + 5 = Q (17)
Following this pattern, the next letter is:
Q (17) + 5 = 22, which corresponds to V.

Third letter position:
Let us examine the positional values of the third letters:
E (5) + 10 = O (15)
O (15) + 10 = Y (25)
Y (25) + 10 = 35 ≡ 9 (since 35 - 26 = 9), which corresponds to I.
Following this pattern, the next letter is:
I (9) + 10 = 19, which corresponds to S.

Fourth letter position:
Let us examine the positional values of the fourth letters:
H (8) + 15 = W (23)
W (23) + 15 = 38 ≡ 12 (since 38 - 26 = 12), which corresponds to L.
L (12) + 15 = 27 ≡ 1 (since 27 - 26 = 1), which corresponds to A.
Following this pattern, the next letter is:
A (1) + 15 = 16, which corresponds to P.

Combining the letters obtained for each position (R, V, S, P), we get the letter-cluster RVSP.