A lively classroom grows through meaningful interaction between teacher and students.
Why B fits: Questions, discussion, feedback, and student participation allow the teacher to respond to learners’ ideas.
Why the others are weaker: A variety of aids alone does not create interaction; silence may suppress participation; strict discipline by itself cannot make learning lively.
Practical point: Interaction should be purposeful and respectful. Students need opportunities to think and speak, while the teacher keeps the activity focused on learning.