In a regression of COMM5005's final exam marks on the number of study hours (measured in hours per day). The slope (b1 ) represents Select one: a. the change in average final exam mark for an hour change in the number of study hours. O b. the predicted mean final exam mark. Oc. the variation of the predicted final exam mark for zero study hours. d. the average final exam mark in COMM5005 when a student did not study at all