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

RMTS, WGAK, BAHC, GUOU, ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
 NMQR, NQYD, NUGP, NYOB, ?

Which letter cluster will replace the question mark (?) to complete the given series?
 ANGE, DSBB, GXWY, ?

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

CABQ, CEJC, CIRO, CMZA, ?

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

ZUPK, YTOJ, ?, WRMH, VQLG

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

TYG, ?, PSM, NPP, LMS

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

HFK, KHM, ?, QLQ, TNS

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

DAJ, GEL, JIN, MMP, ?