Solution

i. Fine hair and mucus act as the first line of defense in the nasal passage, it traps the foreign particles in it. They keep foreign particles away that could cause illness from entering the body. ii. The trachea is supported by c-shaped rings of cartilage which hold them in place when there is less air inside it. Due to this, the walls of trachea do not collapse even when there is a little air. iii. Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs between the alveoli present in lung and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli iv. When you breathe in, or inhale the diaphragm contracts and moves downward. This increases the space in your chest cavity, and the lungs volume would increase. As the volume increases, pressure inside the lung decreases. v. Residual volume is present in the lungs always because it prevents the lungs from collapsing. During breathing cycle there is appropriate time for oxygen to be absorbed and for the carbon dioxide to be released.