The correct answer is metre (m).

Fundamental units are the basic units from which other units are derived. They are not combinations of other units. The International System of Units (SI) defines seven base units:

• Metre (m): Length
• Kilogram (kg): Mass
• Second (s): Time
• Ampere (A): Electric current
• Kelvin (K): Thermodynamic temperature
• Mole (mol): Amount of substance
• Candela (cd): Luminous intensity

Let's examine the other options:

• Pascal (Pa): This is the SI unit of pressure, derived from the base units of newtons per square metre (\(N/m^2\)).
• Watt (W): This is the SI unit of power, derived from the base units of joules per second (\(J/s\)).
• Newton (N): This is the SI unit of force, derived from the base units of kilogram-metres per second squared (\(kg \cdot m/s^2\)).

Therefore, only the metre is a fundamental unit in the SI system.