Elimination by method-family:
Extension methods split into individual-contact methods, group methods, and demonstration methods. Farm and Home Visit (C) is the only purely individual, one-to-one method, so it must map to (I). Between the two demonstrations, Method Demonstration shows the how-to steps of a practice, mapping (B) to (IV), while Result Demonstration showcases the outcome on a farmer's own field, mapping (D) to (II). That leaves Group Discussion (A) matched with (III). This reconstructs the pairing (A)-(III), (B)-(IV), (C)-(I), (D)-(II), matching option 4.