Diane wanted to demonstrate which pruning technique was best for controlling the growth of certain types of shrubs. She selected ten shrubs of the same type and randomly assigned each one to receive one of ten different pruning methods. Two weeks after pruning, she measured the regrowth, in inches, of the shrubs; the pruning method that minimized regrowth was recommended as the best method. Which of the following best describes why this is not a well-designed experiment?

A. The shrubs were not randomly selected.
B. Pruning methods were not randomly assigned to shrubs.
C. Each pruning method was used on only one shrub.
D. Each shrub did not receive all ten pruning methods.
E. Only two treatments should be used in an experiment.