Correct Answer: QBWV

Solution : Given:
P_RSPG_SP_LSPM_S

To fill the series we have to divide it – P_RS / PG_S / P_LS / PM_S
Let's check each option –
First option: CWZO; P C RS / PG W S / P Z LS / PM O S (No, repeated pattern has been found.)
Second option: BWVQ; P B RS / PG W S / P V LS / PM Q S (No, repeated pattern has been found.)
Third option: ABXY; P A RS / PG B S / P X LS / PM Y S (No, repeated pattern has been found.)
Fourth option: QBWV; P Q RS / PG B S / P W LS / PM V S (Here, the first and the fourth letters will remain the same, the second letter of each part is obtained by subtracting 10 from the place value of each letter, and the third letter is obtained by adding 10 to the place value of each letter.)

So, the series is→PQRSPGBSPWLSPMVS. Hence, the fourth option is correct.