Which of the following arrangement of the classroom can bring about the best teaching effect

A．Arranging the desks in straight rows and providing every minute for the students to listen to the teacher.
B．Breaking a class into small groups and letting the students find the group they prefer to stay in.
C．Putting the students in larger classes and allowing them to discuss.
D．Breaking a class into small groups and asking the students to stay in the fixed groups as the teacher arranges.