In the following que stion, a group of letters is given. The letters of each group are related with the letters of the same group by some Logic/Rule/Relation. From the given alte rnatives, se lect a group of letters which follows the same Lo gic/Rule/Relation.
(RST, MML, HGD)

Correct option is D

The logic followed here is:

For, (RST, MML, HGD).

Now,

Let's check one by one with options.

Option A) (PUT, KOL, FHD)

Option B) (PQN, KKF, FEY)

Option C) (MNK, GFC, BZU)

Option D) (TUN, OOF, JIX)

Here, logic followed

Hence, the correct answer is "Option D".