Which action can be explained by physics

Explanation:

The given choices are

• the growth of fungus on a piece of bread .

• the mixing of sodium and chlorine to form common salt .

• the interactions between predators and prey in an ecosystem .

• the pressure of blood exerted on the inner walls of the veins.

The action that can be explained by physics is the last choice:

"The pressure of blood exerted on the inner walls of the veins".

The pressure of blood exerted onthe innter walls of the veins can be described by Continuity Equation which states the mass of a fluid which passes through certain volume is constant, that is, the mass of the fluid remains the same. A deduction of the Continuity Equation is when the fluid passes through greater areas, its pressure is lower and when the fluid passes through sameller areas, its pressure is higher.

That principal can be used to described blood pressure, for example, when people have too much fat, their blood pressure is higher, that is because the area of the veins is smaller, which increases the pressure of the fluid (the blood).

Therefore, the only action that can be explained by physics is the last one.