People who have a vitamin D deficiency also tend to have high blood pressure. 1. Identify the correct interpretation of the statement.

a. Vitamin D deficiency and high blood pressure have a cause-effect relationship in both directions.
b. Taking vitamin D will decrease your likelihood of developing high blood pressure.
c. Vitamin D deficiency causes high blood pressure.
d. Among people who have a vitamin D deficiency, a larger proportion have high blood pressure than not.

2. If there were something genetic which made people simultaneously more susceptible to both vitamin D deficiency an' high blood pressure, that would be an instance of :
a. the placebo effect.
b. common response.
c. confounding.
d. direct causation.