Respiration is the chemical reaction with oxygen by which sugars and starches are converted into energy.

• A. Chemical reaction with oxygen by which sugars and starches are converted into energy
• B. Process of photosynthesis
• C. Process of transpiration
• D. Process of nitrogen fixation

Answer: (A)

Cellular respiration is the process by which carbohydrates like sugars and starches are broken down in the presence of oxygen to release energy stored as ATP. The statement matches this idea because it describes a chemical reaction with oxygen that converts sugars and starches into energy, with carbon dioxide and water produced as byproducts. This aerobic pathway supplies the energy plants and animals need for growth and daily functions. In contrast, photosynthesis uses light energy to synthesize sugars from carbon dioxide and water and releases oxygen; transpiration is simply the loss of water vapor from plant surfaces; nitrogen fixation is the conversion of atmospheric nitrogen into ammonia. So, the described process is cellular respiration, the mechanism by which stored carbohydrates are oxidized to yield usable energy.