Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series. Q _ A D _ R _ K A D P _ Q K A _ P R Q K _ D _ R

K, P, Q, R, D, A, P K, P, Q, R, D, A, Q K, P, R, Q, D, A, P K, P, Q, R, A, D, P

K, P, Q, R, D, A, P

Q K A D P R / Q K A D P R / Q K A D P R / Q K A D P R K, P, Q, R, D, A, P