Concept:Each letter in the cluster advances by one step in the alphabet, and the number increases by 28.
Explanation:From the given pairs:
RX128 → SY156: R to S (+1), X to Y (+1), 128 + 28 = 156.
VL500 → WM528: V to W (+1), L to M (+1), 500 + 28 = 528.
Apply same logic to PD420:
P → Q (next letter), D → E (next letter), 420 + 28 = 448.
Thus, the missing term is QE448.
Answer:Option B. QE448