Concept:Extension teaching methods are grouped according to the number of people reached at one time.
Explanation:The audience size is the main basis for classification.
These methods fall into three types: individual, group, and mass methods.
Individual method guides one farmer or client at a time.
Group method teaches a small gathering of people together.
Mass method spreads information to a large number of people at once.
Since the classification depends on how many learners are involved, the correct choice is audience size.
Answer:D. audience size