Select the related word/letters/number from the given alternatives.
LK : OP :: ? : UV

Let us examine the relationship between the letters in the first pair:
The letters L and O are pairs of opposite letters in the alphabet (Position of L from start=12, Position of O from end=12).

The letters K and P are also pairs of opposite letters (Position of K from start=11, Position of P from end=11).

Following the same logic for the second pair, we need to find the opposite letters for U and V:

The opposite letter of U is F.

The opposite letter of V is E.

Since FE is not in the options, let us look at an alternative positional shift logic:

L(12)→O(15)⟹+3

K(11)→P(16)⟹+5

Applying this reverse shift logic to find the first term from UV:

x+3=U(21)⟹x=18→R

y+5=V(22)⟹y=17→Q

Thus, the missing letters are RQ.