Providing sanitation,housing,food,refrigeration and indoor fires for cooking takes energy,as do the pumping and purifi cation of water and the desalination of seawater for irrigation.

• 假如卫生、住房、食物、制冷以及烹饪等室内用火需要能源的话，那么抽水、净化水以及将海水脱盐以供灌溉也同样需要能源。