A study was conducted to assess whether added calcium in the diet significantly reduces blood pressure. Thirty-two men with high blood pressure were willing to serve as subjects. Each subject took either a white tablet that contains calcium or a dummy pill that looks and tastes like the calcium pill but has no active ingredient. The men did not know which pill they took but the researchers knew. The diastolic blood pressure of each subject was measured after taking the tablet daily for three months. The diastolic blood pressure reductions (in millimeters of mercury) for the group of men who took the calcium pill are given below.

3.1	2.7	3.5	3.3	3.2	2.2	2.6	2.4
0.4	2.6	2.1	2.2	2.8	1.9	4.0	1.4

The variable "blood-pressure reductions" is (select all correct answers)

1. the explanatory variable.
2. a discrete variable.
3. a confounding variable.
4. a quantitative variable.
5. the response variable.
6. a continuous variable.
7. a qualitative variable.