Urethral meatus refers to the:

Options

A. urinogenital duct
B. opening of vas deferens into urethra
C. external opening of the urinogenital duct
D. muscles surrounding the urinogenital duct

Explanation

### Step-by-Step Solution:

1. **Understanding the Term "Meatus":**
- The term "meatus" refers to a natural opening or canal in the body. It is important to recognize that it denotes an external opening.

2. **Defining Urethral Meatus:**
- The urethral meatus specifically refers to the opening of the urethra, which is part of the urinogenital tract. This is the passage through which urine and, in males, semen are expelled from the body.

3. **Function of the Urethral Meatus in Males:**
- In males, the urethra serves a dual function: it carries urine from the bladder and semen from the reproductive system. The urethral meatus is the external opening where both of these substances exit the body.

4. **Analyzing the Options:**
- **Option 1:** "Urinogenital duct" - This is incorrect because the urethral meatus is not the duct itself; it is the opening of the duct.
- **Option 2:** "Opening of vast difference into the urethra" - This is also incorrect because the vast difference (vas deferens) connects to the urethra internally, not as an external opening.
- **Option 3:** "External opening of the urinogenital duct" - This is the correct option, as it accurately describes the urethral meatus as the external opening of the duct.
- **Option 4:** "Muscles surrounding urinogenital duct" - This is incorrect because the urethral meatus is not a muscle; it is an opening.

5. **Conclusion:**
- The correct answer is **Option 3: External opening of the urinogenital duct**.