Stella is interested in determining whether people have gotten more or less exercise since going under social distancing protocols. Zhe asks people, "Please estimate the number of hours of exercise you got each week before social distancing took effect" and then asks, "Please estimate the number of hours of exercise you got each week after social distancing took effect." Both of these variables are positively skewed. What are zer independent and dependent variables? Question 7 options: a) Zer independent variable is exercise; zer dependent variable is time (before/after social distancing). b) Zer independent variable is time (before/after social distancing); zer dependent variable is exercise. c) Zer independent variable is stress before; zer dependent variable is stress after. d) Zer independent variable is stress after; zer dependent variable is stress before