**Core Concept:** Diuretics are medications that increase urine production and volume by promoting the excretion of sodium and water from the body, thereby decreasing blood volume and pressure. They are commonly used for the treatment of hypertension and congestive heart failure.

**Why the Correct Answer is Right:** Diuretics work by inhibiting the action of the hormone aldosterone, which is responsible for retaining sodium and water in the body. By reducing the amount of sodium and water retained, diuretics increase urine production and volume.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it does not reflect the primary action of diuretics. Diuretics do not directly cause loss of potassium.
B. This option may be tempting due to the mention of potassium, but it is incorrect because diuretics actually retain potassium by reducing the amount of sodium being filtered in the kidneys, thus decreasing the reabsorption of potassium.
C. This option is incorrect because, while diuretics may cause a temporary increase in blood pressure due to reduced blood volume, their primary action is to decrease sodium and water retention, leading to a decrease in blood pressure over time.
D. This option is incorrect because diuretics do not cause an increase in blood glucose levels. Instead, they help in reducing blood volume and pressure, thereby indirectly benefiting patients with diabetes and other cardiovascular conditions.

**Clinical Pearl:** Diuretic therapy should be carefully monitored in patients with diabetes mellitus, as excessive diuretic use may lead to hyperglycemia and worsening of glycemic control.

**Correct Answer:** C. Diuretics cause a decrease in blood pressure due to reduced blood volume and the subsequent decrease in cardiac output and systemic vascular resistance.