The correct answer is option-1: 4%. When we exhale air, it contains approximately 4% carbon dioxide. This is because our body processes the oxygen we inhale and converts it into carbon dioxide as a waste product. The carbon dioxide is then expelled from our body through exhalation. It is worth noting that the carbon dioxide levels can vary depending on factors such as physical activity and overall health. However, on average, the carbon dioxide content in exhaled air is around 4%.