i dontreally know but i would say recycling
Farmers used crop rotation to keep the earth fertile.
nothing
3 percent is useable to humans and land animals
The Sun is the ultimate source of all useable energy on Earth.
The Sun is the ultimate source of all useable energy on Earth.
The Sun is the ultimate source of all useable energy on Earth.
The Sun is the ultimate source of all useable energy on Earth.
No.
rotation of the crops.
The sun. In fact nearly all useable energy on Earth derives eventually from the Sun.
In the block that contains its definition./* i isn't useable here */{ int i; /* i is useable here */ }/* i isn't useable here */
1 percent of fresh water is useable