Janet is testing the effectiveness of four different plant foods. She plants four identical seeds in four identical pots, supply
ing each with a different type of plant food. After six weeks she finds that the four plants have grown to different heights. Can Janet conclude that food W is the most effective of the four plant foods?
A. Yes; since the plant that was fed food W grew to the greatest height, the only explanation is that food W is the most effective.
B. No; Janet needs to test many more different types of plant food before she can reach that conclusion.
C. Yes; 18 inches is the tallest a plant of that species has ever grown.
D. No; Janet needs to conduct repeated trials on many different plants before she can make that conclusion.
