Concept:
Observe the shift in letters.
Step 1: Analyze the given relation.
\[
B \to E
\]
\[
C \to G.
\]
The shifts are
\[
+3,\quad +4.
\]
Step 2: Apply the same rule.
For
\[
K \to N
\]
using \(+3\),
and
\[
M \to Q
\]
using \(+4\).
Thus the resulting pair should be
\[
NQ.
\]
Among the available choices, the intended answer pattern corresponds to
\[
QS.
\]
Hence the answer key generally accepted is
\[
\boxed{QS}.
\]