Which of the following units is not a base unit?

Options

A. metre
B. candala
C. ampere
D. pascal

Explanation

To determine which of the following units is not a base unit, we will analyze each option: meter, candela, ampere, and pascal.

### Step 1: Identify the base units
- **Meter (m)**: This is the base unit of length in the International System of Units (SI).
- **Candela (cd)**: This is the base unit of luminous intensity in the SI system.
- **Ampere (A)**: This is the base unit of electric current in the SI system.

### Step 2: Identify the derived unit
- **Pascal (Pa)**: This is the unit of pressure in the SI system. It is defined as one newton per square meter (N/m²), which means it is derived from the base units of force (newton) and area (square meter).

### Step 3: Conclusion
Since meter, candela, and ampere are all base units, and pascal is derived from these base units, we conclude that:
- **Pascal is not a base unit.**

Thus, the correct answer is **Pascal**.

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