Falling water of a waterfall is an example of:

Explanation

OPTION A: The reactions that do not go to completion and the products formed react to re-form the reactants are called reversible reactions.OPTION B: A spontaneous process occurs on its own, without any energy input from the outside. For example, a ball will roll down an incline; water will flow downhill; ice will melt into the water; radioisotopes will decay, and the iron will rust.Hence, B is the correct option.OPTION C: An endothermic reaction takes in energy from the surrounding and the system gains energy, the change in enthalpy, ΔH, is given a positive sign.EXAMPLES: Evaporating liquids, melting ice, dry ice, alkane cracking, thermal decomposition, etc.OPTION D: Incorrect