Which of the following is a system of the human body?

• A. Photosynthetic system
• B. Combustion system
• C. Digestive system
• D. Respiratory system

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of a 'system' in the human body. A system is a group of organs that work together to perform specific functions essential for maintaining homeostasis and overall health.
2. Step 2: Review the options provided in the question. The 'Photosynthetic system' and 'Combustion system' are not systems of the human body. Photosynthesis is a process used by plants to convert sunlight into energy, and combustion refers to a chemical reaction involving burning, neither of which are relevant to human anatomy.
3. Step 3: Identify the correct systems from the options. The 'Digestive system' is responsible for breaking down food into nutrients that the body can absorb and use for energy, growth, and repair. The 'Respiratory system' facilitates gas exchange, allowing oxygen to enter the blood and carbon dioxide to be expelled.
4. Step 4: Understand the roles of the Digestive and Respiratory systems. The Digestive system includes organs such as the stomach, intestines, and liver, while the Respiratory system includes the lungs, trachea, and diaphragm. Both systems are vital for sustaining life.
5. Step 5: Conclude that the Digestive system and Respiratory system are correct answers because they are recognized systems of the human body, unlike the Photosynthetic and Combustion systems, which are unrelated to human physiology.