Answer:
<u>d. Swimming for 40 minutes.</u>
Explanation:
<u>Cardio workout</u> is also known as <u>cardiovascular workout</u> or <u>aerobic exercises</u>. It involves <u>exercises in which increasing heart rate is involved</u>. These exercises utilize the energy generating aerobic processes of the body. Such exercises help in maintaining a fit cardiovascular and pulmonary system.
From the given options,
<u>a. Doing abdominal exercises for 45 minutes.</u>
This is an example of strength training.
<u>b. Lifting weights for one hour.</u>
This is an example of weight training which is a type of strength training.
<u>c. Stretching for 30 minutes</u>.
This is an example of flexibility training.
<u>d. Swimming for 40 minutes.</u>
This is an example of cardio workout (aerobic exercise/endurance training).
This is the correct option as swimming entails increasing heart rate. Other cardio workouts are running, jogging, cycling and walking.