A college biology teacher wants to know whether being tutored at the study lab will help her students score higher on their final exam. She randomly selects 60 students from among the four sections of introductory biology that she teaches. Then she randomly divides them into groups of 30 students each Group A will be tutored at the study lab, and group b will not be tutored at the study lab. After all 60 students take their final exam, she will compare their results. Which of these are the treatments in this experiment?

a. taking a morning biology class and taking an afternoon biology class
b. being one of the 60 students selected and not being one of the 60 students selected
c. having taken high school biology and not having taken high school biology
d. being tutored at the study lab and not being tutored at the study lab