Assertion (A) is correct: In extension education, using multiple extension techniques (e.g., demonstrations, workshops, field visits, media campaigns, and group discussions) typically leads to higher adoption rates of new practices compared to relying on a single method. This is because varied methods cater to diverse learning styles, reinforce messages, and increase engagement among learners, such as farmers adopting new agricultural practices. Reason (R) is incorrect: While multiple methods are often more effective, a single extension technique (e.g., a well-executed demonstration) can still be impactful and far from "useless" depending on the context, audience, and execution. The absolute claim that a single technique is useless exaggerates and does not accurately explain why multiple methods enhance adoption. Thus, option (2) is correct, as (A) is true, but (R) is false.