Which letter-cluster will replace the question mark (?) to complete the given series?

MBTN, KCSP, IDRR, ?, EFPV

Which letter-cluster will replace the question mark (?) to complete the given series?

DMT, JOB, PQJ, VSR, ?

Select the letter that will replace the question mark (?) in the given letter series.
 a, d, h, n, ?

Which of the following terms will replace the question mark (?) in the given series?
 FOX  ?   JSX  LUX  NWX

Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it.
c_bba_cab_ac_ab_ac