Bernoulli`s principle is based on the principle of conservation of energy, which states that energy cannot be created or destroyed but can only be transferred or converted from one form to another.

Option 1, conservation of mass, refers to the principle that mass is conserved in a closed system. While mass plays a role in Bernoulli`s principle, it is not the primary basis for the principle.

Option 2, conservation of momentum, states that the total momentum of a system remains constant unless acted upon by an external force. While momentum is involved in fluid flow, it is not the fundamental principle behind Bernoulli`s principle.

Option 3, conservation of angular momentum, states that the total angular momentum of a system remains constant in the absence of torque. Angular momentum does not directly apply to Bernoulli`s principle.

Therefore, option 4, conservation of energy, is the correct answer. Bernoulli`s principle describes the relationship between the pressure, velocity, and height of a fluid in steady flow. It states that as the velocity of a fluid increases, the pressure decreases, and vice versa, while the sum of the kinetic and potential energies remains constant.