After we exercise, several physiological changes occur in our body to meet the increased demands of physical activity. These changes include increased oxygen consumption, energy expenditure, and carbon dioxide production. Therefore, all of the given options are correct.

Increased Oxygen Consumption
During exercise, our muscles require more energy to contract and perform work. This increased energy demand is met by an increased oxygen consumption. Oxygen is necessary for the breakdown of glucose and fatty acids in our cells through a process called aerobic respiration. This process produces adenosine triphosphate (ATP), which is the primary energy source for our muscles. Therefore, our body needs more oxygen to fuel this energy production during exercise.

Energy Replacement
As we exercise, our body utilizes stored energy sources such as glycogen (in the muscles and liver) and adipose tissue (body fat). These energy sources are broken down to release ATP and provide energy for muscle contractions. After exercise, our body needs to replenish these energy stores to prepare for future physical activity. This is achieved through the consumption of carbohydrates and fats in our diet. These nutrients are converted into glycogen and stored in the muscles and liver for later use.

Carbon Dioxide Elimination
During exercise, our muscles produce carbon dioxide as a byproduct of ATP production through aerobic respiration. This carbon dioxide needs to be eliminated from our body to maintain proper pH levels and prevent the buildup of waste products. The excess carbon dioxide is transported in our bloodstream to the lungs, where it is exhaled. This process is known as respiration, and it helps to maintain the balance of carbon dioxide and oxygen levels in our body.

In summary, after exercise, our body requires more oxygen to meet the increased energy demands, it needs to replace the energy used by replenishing glycogen stores, and it needs to eliminate excess carbon dioxide produced during exercise. Therefore, all of the given options (a, b, and c) are correct.