Question

what is aldosterone and what does it do?
hormone that causes kidneys to excrete sodium and water, leading to decrease in blood volume and pressure
hormone that causes kidneys to retain sodium and water, leading to decrease in blood volume and pressure
hormone that causes kidneys to retain sodium and water, leading to increase in blood volume and pressure
hormone that causes kidneys to retain potassium and water, leading to decrease in blood volume and pressure
hormone that causes kidneys to excrete potassium and water, leading to increase in blood volume and pressure

Explanation:

Aldosterone is a hormone secreted by the adrenal cortex. Its main function is to act on the kidneys. By promoting the re - absorption of sodium ($Na^{+}$) and water ($H_{2}O$) in the renal tubules, it increases the blood volume. According to the principle of fluid mechanics in the cardiovascular system, an increase in blood volume leads to an increase in blood pressure. Also, it promotes the excretion of potassium ($K^{+}$).

Answer:

Hormone that causes kidneys to retain sodium and water, leading to increase in blood volume and pressure