The fundamental unit is :

Options

A. newton
B. pascal
C. hertz
D. second

Explanation

To determine which of the given options is a fundamental unit, we will analyze each option based on whether it is a fundamental unit or a derived unit.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- Option 1: Newton
- Option 2: Pascal
- Option 3: Hertz
- Option 4: Second

2. **Analyze Option 1: Newton**:
- Newton (N) is the SI unit of force.
- Force is a derived quantity because it is calculated using mass and acceleration (F = m*a).
- Therefore, Newton is a derived unit.

3. **Analyze Option 2: Pascal**:
- Pascal (Pa) is the SI unit of pressure.
- Pressure is also a derived quantity, defined as force per unit area (P = F/A).
- Thus, Pascal is a derived unit.

4. **Analyze Option 3: Hertz**:
- Hertz (Hz) is the SI unit of frequency.
- Frequency is defined as the reciprocal of the time period and is derived from time.
- Hence, Hertz is a derived unit.

5. **Analyze Option 4: Second**:
- Second (s) is the SI unit of time.
- Time is a fundamental quantity and does not depend on other quantities.
- Therefore, second is a fundamental unit.

6. **Conclusion**:
- Among the given options, only "Second" is a fundamental unit.
- Thus, the correct answer is **Option D: Second**.