All over the world forests are safeguarding the health of the planet itself. They do this

All over the world, forests are safeguarding the health of the planet itself. They do this【C1】______protecting the soil, providing water and【C2】______the climate. Trees【C3】______soil to mountainsides. Hills【C4】______the trees have been felled lose 500 times as【C5】______soil a year as those with trees.

Trees catch and【C6】______rainwater. Their leaves break the impact【C7】______the rains, robbing them of【C8】______destructive power. The roots of trees allow the water to go into the soil,【C9】______gradually releases it to flow down rivers and refill ground-water reserves. Where there are no【C10】______, the rains run in sheets of water off the land,【C11】______the soil with there Land【C12】______with trees and other plants【C13】______20 times more rainwater than【C14】______earth. As they grow, trees absorb carbon dioxide, the main【C15】______of the "greenhouse effect", which【C16】______irreversibly to change the world"s climate. Together, the world"s trees, plants and soils contain three times as much carbon as【C17】______is in the atmosphere.

The world"s forests【C18】______the vast majority of its animal and plant species. The tropical rainforests【C19】______have well over half of them,【C20】______they cover only about 6% of the Earth"s land surface.

【C1】

A．for

B．from

C．by

D．with