One of these statements is true about slavery. which one is it?
a. it began with the spanish and portuguese transatlantic slave trade.
b. it had existed all over the world in various forms for thousands of years.
c. it existed only in africa before the sixteenth century.
d. it first began in africa in the 1500s and then spread to others parts of the world.

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy