Case 2 : the biological process involved in the removal of harmful metabolic wastes from the bosy is called excertion .Different organisms use varied strategies to do this Many unicellular organisms remove these wastes by simple diffusion from the body surface into the surrounding water while complex multicellular organisms use specialised organs to perform the same function .
Which of the following statements (s) is (are) true about excretion in human beings ?
(I) Urine is stored in the urethra until the urge of passing it out .
(II) Kidneys are the primary excretory organs .
(III) The bladder is muscular so it under nervous control .
(IV) Each kidney has large numbers of filtration units called nephrons .

Options

A. (I) and (II) only
B. (I) and (III) only
C. (II) , (III) and (IV)
D. (II) and (IV) only

Explanation

To determine which statements about excretion in human beings are true, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement I: Urine is stored in the urethra until the urge of passing it out.**
- This statement is **false**. Urine is not stored in the urethra; it is stored in the urinary bladder. The urethra is the tube through which urine is expelled from the body.

2. **Statement II: Kidneys are the primary excretory organs.**
- This statement is **true**. The kidneys are indeed the primary excretory organs in humans. They filter blood to produce urine, which contains waste products.

3. **Statement III: The bladder is muscular so it is under nervous control.**
- This statement is **true**. The urinary bladder is a muscular organ that is controlled by the nervous system. It contracts to expel urine and is under both voluntary and involuntary control.

4. **Statement IV: Each kidney has large numbers of filtration units called nephrons.**
- This statement is **true**. Each kidney contains approximately one million nephrons, which are the functional units responsible for filtering blood and forming urine.

### Conclusion:
- The true statements about excretion in human beings are **II, III, and IV**.

### Summary of True Statements:
- **II**: Kidneys are the primary excretory organs. (True)
- **III**: The bladder is muscular so it is under nervous control. (True)
- **IV**: Each kidney has large numbers of filtration units called nephrons. (True)