The human body has an organ A which acts as a pump. The pump A pumps a liquid B into the whole body continuously. The liquid B supplies the useful substances C and D to all the body cells and removes a waste E from the body cells.
What are organ A ?

Answer

**Step-by-Step Solution:**

1. **Identify the Organ (A):** The question states that there is an organ in the human body that acts as a pump. In humans, the organ that functions as a pump is the heart. Therefore, organ A is the heart.

2. **Identify the Liquid (B):** The organ A (heart) pumps a liquid throughout the body. In the human body, the liquid that is pumped by the heart is blood. Thus, liquid B is blood.

3. **Identify Useful Substances (C and D):** The question mentions that the liquid B (blood) supplies useful substances to the body cells. Two important substances that blood supplies are:
- C: Oxygen (which is essential for cellular respiration)
- D: Nutrients (such as glucose, vitamins, and minerals that are necessary for energy and growth)

4. **Identify the Waste (E):** The question also states that the liquid B (blood) removes waste from the body cells. A common waste product removed by blood is nitrogenous waste, which includes substances like urea. Therefore, waste E is nitrogenous waste.

5. **Final Answer:** To summarize, the organ A is the heart, the liquid B is blood, the useful substances C and D are oxygen and nutrients, respectively, and the waste E is nitrogenous waste.

**Final Answer:** Organ A is the heart.

---