**Core Concept:** Cardiac index (CI) is a measure of how efficiently the heart is pumping blood per unit body surface area. It is calculated as cardiac output (CO) divided by body surface area (BSA).

**Why the Correct Answer is Right:** Cardiac output is the volume of blood pumped by the heart in one minute, and body surface area is a measure of the total area of the body exposed to the environment. By dividing cardiac output by body surface area, we normalize the cardiac output to the size of the patient, allowing us to compare cardiac function between individuals with different body sizes.

**Why Each Wrong Option is Incorrect:**

A. This explanation is incorrect because it does not address the relationship between cardiac output and body surface area in determining cardiac index.
B. This explanation is incorrect because it does not provide the actual calculation of cardiac index.
C. This explanation is incorrect as it misinterprets the relationship between cardiac output, body surface area, and cardiac index.
D. This explanation is incorrect as it is a duplicate of option A and does not address the relationship between cardiac output and body surface area in determining cardiac index.

**Clinical Pearl / High-Yield Fact:** A high cardiac index is generally considered favorable as it indicates efficient cardiac function, while a low cardiac index indicates reduced cardiac function and may be associated with poor tissue perfusion and organ dysfunction. In clinical practice, cardiac index is often calculated or estimated to assess cardiac performance in various conditions, such as sepsis, shock, or heart failure.

**Correct Answer:** C. 0.33 L/min/m².

To calculate cardiac index, we use the formula:

Cardiac Index (CI) = Cardiac Output (CO) / Body Surface Area (BSA)

In this question, the provided values are:

Cardiac Output (CO): 5 liters/minute
Body Surface Area (BSA): 1.7 m²

Plugging these values into the formula, we get:

Cardiac Index (CI) = (5 L/min) / (1.7 m²) = 0.33 L/min/m²

So, the correct answer is option C: 0.33 L/min/m².