Write the next sentence in the following story.

How to condition your body to need less sleep
Exercise.
If you expect to function without sleep you'll have to build up your body's overall strength. Exercising three or four times a week can build your overall strength and stamina, resulting in you needing less sleep.

Pick your answer from: i. Thirty minutes of vigorous exercise a day is one estimate you might have to make to build up muscles and keep them functioning properly. As the standard holiday bonus, jogging, biking, and yoga can increase your stamina.. ii. The amount of exercise you do will depend on your age and activity level. Experts recommend 150 minutes per week of aerobic exercise three times per week.. iii. Exercise has been shown to relieve some of the anxiety associated with sleep, so give yourself a break from body work and stick to a regular routine. Both jogging, rowing and other walking exercises increase your range of motion and prevent you from having to constantly get out of bed.. iv. Focus on aerobics, like running or jogging, swimming, as well as mild weight training, such as lifting weights, doing push or sit ups, and pilates. Exercise in the afternoon is ideal as your overall sleep quality at night improves... The answer should be
iv.