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

ZXE ZWD ZVC ? ZTA

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
 RTM, VZX, ZFI, DLT, ?

The second number in the given number pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) are followed in all the number pairs, EXCEPT one. Find that odd number pair.

Directions: Study the following information carefully and answer the questions given below:
 Nine boxes named P, Q, R, S, T, U, V, W and X are placed one above the other but not necessarily in the same order. Only five boxes are placed between P and R. T is placed immediately above R. Only three boxes are placed between T and S. As many boxes are placed between P and S as between Q and T. U is placed below Q, but not at the bottom. More than four boxes are placed between T and U. One box is placed between U and V. Box X is placed above box W.

Which box is placed at the bottom?

The second number in the given number pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) are followed in all the number pairs EXCEPT one. Find that odd number pair.

Four clusters have been given out of which three are alike in some manner and one is different. Select the one that is different.

Option

Select the option that is related to the fifth letter-cluster in the same way as the second letter-cluster is related to the first letter-cluster and the fourth letter-cluster is related to the third letter-cluster.
 COOK : DQPM :: DOWN : EQXP :: ONLY : ?

Four clusters have been given out of which three are alike in some manner and one is different. Select the one that is different.

Option