The process of breathing involves inspiration and expiration. In normal conditions, inspiration takes about 2 seconds and expiration takes about 3 seconds. On average, an adult human breathes about 16 times in a minute. During inspiration, the diaphragm and external intercostal muscles contract to increase the volume of the thoracic cavity, which causes air to flow into the lungs. During expiration, the diaphragm and external intercostal muscles relax, which decreases the volume of the thoracic cavity and causes air to flow out of the lungs. Therefore, the correct option is A) Inspiration 2 sec and expiration 3 sec.