Explanation:

- The amount of blood pumped by the heart per minute is called cardiac output.

- In a normal adult at rest, the average cardiac output is about 5 litres per minute.

- Option 1: 1 litre – This is too low for a normal adult; it would not meet the body's needs.

- Option 2: 3 litres – Still below the average resting requirement.

- Option 3: 5 litres – This is the correct average cardiac output for a healthy adult at rest.

- Option 4: 7 litres – This is higher than normal for rest and may occur during intense exercise, but not at rest.