SORU: aşağıdaki parçaya göre cevaplayınız
The major focus of the passage is on ----.
When sunlight heats the earth, it also heats the
atmosphere. As hot air rises, cooler and heavier air
rushes in to fill its place, thus creating wind. For more
than 2,000 years, people have captured this energy
with windmills and used it to do useful things, such as
grinding grain or pumping water. By the late 19th
century, windmills were also being used to produce
electricity, mostly in rural areas. Compared with
traditional windmills, however, modern wind turbines
are far more efficient.