Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series. _ msk _ prm _ kt _ r _ s _ tpr _ skt _

r,s,t,p,m,k,m,p r,t,s,p,m,m,m,p r,t,s,p,m,k,m,p r,t,s,p,m,k,m,p

r,t,s,p,m,k,m,p

r m s k t p / r m s k t p / r m s k t p / r m s k t p r , t , s , p , m , k , m , p