Correct Answer: PSQPRS

Solution : Given:
_RQ_PR_S_ _QSPRQ_

Check the order of the letters in the given series.
To fill the series we have to divide the series –
_RQ_ / PR_S / _ _QS / PRQ_
Let's check the options –
First option: PQRSPR; P RQ Q / PR R S / SP QS / PRQ R (No repeated pattern has been found.)
Second option: PSQPRS​​​​​; P RQ S / PR Q S / PR QS / PRQ S (PRQS is the repeated letter cluster.)
Third option: PSRQPS; P RQ S / PR R S / QP QS / PRQ S (No repeated pattern has been found.)
Fourth option: PRQSPS; P RQ R / PR Q S / SP QS / PRQ S (No repeated pattern has been found.)

So, PRQS is the repeated letter cluster in the second option. Hence, the second option is correct.