SORU: aşağıdaki parçada numaralanmış yerlereuygun düşen sözcük ya da ifadeyi bulunuz
Early machines, such as axes and ramps, relied on
human muscle power to make them work. Then people
started using animals to work many simple machines.
Animals, (16)---- oxen and horses, could carry, pull and
lift much heavier loads than people could. (17)----, people
realized they could capture the energy of the wind or
flowing water by using windmills and water-wheels.
These became the first machines (18)---- power that in
turn was used to make other machines work. This
energy was used to do such things as grinding grain to
make flour or pumping water (19)---- underground.
Today, wind and water energy are still (20)---- to
generate electricity, which we use to light and power our
homes, schools, offices and factories.