Some educators have had remarkable success with an unusual approach to science education. For example, a physics lesson on the properties of waves might begin by plucking guitar strings. After observing the strings vibrate, students would begin to apply names to the phenomena they had witnessed, such as frequency and amplitude. Only after fully understanding these real-life concepts would they begin to apply abstract terms and equations to the phenomena. Which one of the following principles is best illustrated by the example above? ['Familiarity with phenomena facilitates the learning of more formal treatments of these phenomena.', 'Students are unable to form abstract concepts concerning phenomena until they become familiar with these phenomena.', 'Students will understand abstract terms only if they are applicable to phenomena they have observed.', 'Students learn best when teachers appeal to the interests of their students.']