Briana designs a science fair experiment where she drops a basketball, tennis ball and golf ball from three different heights. She conducts ten trials where she drops each type of ball from a height of 100 cm, 80 cm, and 50 cm. She records the height of each ball after it bounces off the ground. Briana's teacher hands her science fair proposal back to her and asks her to fix her mistake. How should she fix her experiment? A-Include only one tested (independent) variable in the experiment.

B-Include research about the composition of each ball.

C-Include the average of her trials in her data chart.

D-Include a soccer and golf ball in her test.