Concept:Mass methods of extension are used to communicate with a wide audience at the same time using public media.
Explanation:Individual methods involve direct contact with one person, such as telephone calls or informal contacts.
Group methods involve a small set of people, such as home visits and demonstrations.
Letters reach only one person, so they are not a mass method.
Newspapers, radio, and posters can all reach many people at once.
Among the given pairs, only radio and posters are both true mass methods of extension.
Answer:D. Radio and posters