Research Question: What is the combined effect of fertilizer and watering on cherry tomato plants? Planters were built that each contained 10 cherry tomato plants. Each planter was identical except that it received a different treatment of water and fertilizer than the other planters. Treatments consisted of a combination of one of four watering schedules and one of three fertilizer concentrations. The plants were tended according to these treatments and after 65 days the average number and weight of the tomatoes per plant were measured for each treatment group. Which of the following is an explanatory variable in this study? Check all that apply. Number of plants per planter Watering schedule Fertilizer schedule Number of tomatoes per plant Watering schedule Number of days of treatment