Jamal and Billy are testing paper airplanes to see which design makes a plane fly farther. Jamal's design has straight wings and Billy's has bent wings. They stood side by side and each threw their planes at the same time. They did this six times, measuring how far each plane went from the starting line in meters. They decided that Billy's design with bent wings travels farther. What should they do next to see if their results are valid?
A. Have other friends try the same experiment.
B. Have them throw planes in different locations.
C. Have them throw with their eyes shut each time.
D. Have Billy bend the wings up even more on his plane.