Which One of the Following Classrooms Best Reflects Effective Classroom

Which one of the following classrooms best reflects effective classroom management as the textbook uses the term?

A) Mr. Alton's students are busily working on their math assignments in groups of three or four students each. When groups get a bit noisy in their discussions of particular problems,Mr. Alton reminds them to use their "indoor" voices.
B) While Ms. Berg works with a reading group,most of her other students are doing their assigned seatwork,although a handful of them are giggling in the corner about something that happened on the school bus earlier.
C) While Ms. Carrera sits at her desk in the front of the classroom,her students are doing assignments independently at their desks. As long as the classroom is quiet,she overlooks the students' whispering,note passing,and mindless doodling.
D) In his physical education class,Mr. Dupuis works with the students who seem truly interested in learning the long jump. Those students who don't want to try the jump are allowed to sit on the sidelines and talk quietly among themselves.