Перевести надо с , hlp trees give off a lot of oxygen into the air because they are very big plants with a lot of leaves on each. but people and animals use a lot of oxygen to breathe. for example, a hectare of pine forest gives oxygen enough for ten people only. it will be necessary to have 1,000 square kilometres of forest for ten million people. now there are not enough forests and plants on the earth for the industry, house building and agriculture.
