Which One of the Following Teaching Strategies Best Illustrates the Concept

Which one of the following teaching strategies best illustrates the concept press for understanding?

A) Mr. Andersen asks students to explain and justify their approach to solving complex problems.
B) Ms. Blumenfeld uses a concrete model of the solar system to explain why we have summer and winter.
C) Mr. Carowsky has students take true-false quizzes on a certain topic until they earn a score of 90% or higher.
D) Ms. dePalma gives an abstract lecture on the concepts of momentum and inertia and then follows it up with several examples of how these concepts can be seen in students' everyday lives.