5. A group of students is making paper airplanes. They think that the kind of paper and the design of the airplane may affect how far each paper airplane flies. The students first test if the kind of paper affects how far the airplane flies. They make several airplanes out of different kinds of paper, using the same design. Why is it important that all the airplanes have the same design? A. By using the same design, the students can leam about the effect of the design. B. If they do not use the same design, the students cannot learn about the effect of the paper. C. By using the same design, the students can learn about both the effect of the design and the effect of the paper. D. It is NOT important for the airplanes to have the same design because the students are not testing the effect of the design.