Think about the following examples of homeostatic regulation: in response to an increase in plasma k⁺ concentrations, the hormone aldosterone brings k⁺ levels back to normal. in response to a decrease in plasma ca²⁺ concentrations, parathyroid hormone brings ca²⁺ levels back to normal. which of the statements below is true?
a. both are examples of negative feedback regulation.
b. the second example illustrates positive feedback because the regulated variable (plasma ca²⁺) increases.
c. only the first example demonstrates negative feedback because the regulated variable (plasma k⁺) is lowered as a result.
d. both examples demonstrate positive feedback, because the alteration in the regulated variable results in an increase in secretion of the regulating hormone.