Which situation best demonstrates the law of conservation of energy?

a
a long distance runner conserving her energy to sprint at the end of the race
b
the potential energy of a ball being dropped from a cliff being converted to kinetic energy
c
ice water transforming into liquid water when it absorbs heat energy
d
batteries being able to store potential energy over a long period of time

b - the potential energy of a ball being dropped from a cliff being converted to kinetic energy.