Human Excretory System

To solve the problem, we need to identify which part of the nephron functions as the filtration unit.

1. Filtration Unit in the Kidney:
The filtration unit of the kidney is actually the Glomerulus. It is a network of capillaries located within the **Bowman's capsule**.

2. Explanation:
The process of filtration in the kidney begins when blood flows into the glomerulus from the renal artery. The pressure forces water, small molecules, and waste products from the blood to pass into the Bowman's capsule, which collects the filtrate.

Final Answer:
The correct answer is .

To solve this question, we need to identify the secondary excretory function performed by the lungs.

1. Understanding Lung Functions:
The primary function of the lungs is respiration, which involves gas exchange—taking in oxygen (O₂) and expelling carbon dioxide (CO₂).

2. Secondary Excretory Function:
Apart from their primary respiratory function, lungs also play an excretory role by eliminating gaseous metabolic waste products, specifically carbon dioxide (CO₂) and water vapor (H₂O).

3. Evaluating Given Options:

• (1) Removal of CO₂ and Water – Correct, lungs excrete carbon dioxide and water vapor.
• (2) Elimination of Sebum – Incorrect, sebum is secreted by sebaceous glands in the skin.
• (3) Urea formation – Incorrect, urea is formed in the liver, not lungs.
• (4) Excretion of excess salts – Incorrect, excess salts are primarily removed by kidneys and sweat glands.

Final Answer:
The correct answer is (A) Removal of CO₂ and Water.