Correct Answer: Q S R R P R Q

Solution : Given:
P _ R R _ P Q _ _ S _ Q R _ S P _ R R S

To fill the series we have to divide the series –  P _ R R _ / P Q _ _ S / _ Q R _ S / P _ R R S
Let's check each option –
First option: R Q P Q R S Q; P R R R Q / P Q P Q S / R Q R S S / P Q R R S (No repeated pattern has been found)
Second option: S Q R R Q P R; P S R R Q / P Q R R S / Q Q R P S / P R R R S (No repeated pattern has been found)
Third option: S Q Q R R P Q; P S R R Q / P Q Q R S / R Q R P S / P Q R R S (No repeated pattern has been found)
Fourth option: Q S R R P R Q; P Q R R S / P Q R R S / P Q R R S / P Q R R S (PQRRS is repeated in the series)

So, the series becomes→P Q R R S P Q R R S P Q R R S P Q R R S. Hence, the fourth option is correct.