Four letter-cluster have been given out of which three are alike in some manner, while one is different. Choose the odd one.

We know that Alphabet position A = 1, B=2, C=3 .......... Z=26 

  DGK   is written as alphabet position = 4 7 11 

the pattern is follow 4+7 = 11 (K)

MLY is written as alphabet positon = 13 12 25

pattern is follow 13+12= 25  

and Similar  QFW is written as alphabet positon = 17 6 23 

pattern is follow 17+6 = 23

But ENR is written as = 5 14 18

from the above pattern we check 5+14 = 19 which is not staisfied the above pattern 

therefore  (C) is different from another option .