Hydraulic brakes are based on

• Pascal's law work as the principle for hydraulic brake operation. 
• This law states that if fluid is under pressure, it moves consistently in all directions. 
• As a result, when we exert force on a small piston, pressure is generated that is transferred to a larger piston via the fluid. 
• This greater force causes uniform braking to be given to all four wheels. 
• They are referred to as hydraulic brakes because hydraulic pressure produces the braking force. 
• Since liquids are incompressible, they are employed in place of gases.

Hence the correct answer is Pascal's law.