A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
SR, ON, ?, GF

Let's observe the positional values of the pairs:
SR→S(19),R(18)

ON→O(15),N(14)

GF→G(7),F(6)

Notice the pattern between consecutive pairs:

From first letter of first pair to first letter of second pair: 19−4=15 (O)

Following the −4 pattern: 15−4=11, which is K.

Checking consistency: 11−4=7 (G), which matches the last term.

Similarly, for the second letters:

From second letter of first pair to second letter of second pair: 18−4=14 (N)

Following the −4 pattern: 14−4=10, which is J.

Checking consistency: 10−4=6 (F), which matches the last term.

Thus, the missing term is KJ.