All over the world, forests are safeguarding the health of the planet itself. They do this (26) protecting the soil, providing water and (27) the climate. Trees (28) soil to mountainsides. Hills (29) the trees have been felled lose 500 times as (30) soil a year as those with trees. Trees catch and (31) rainwater. Their leaves break the impact (32) the rains, robbing them of (33) destructive power. The roots of trees allow the water to go into the soil, (34) gradually releases it to flow down rivers and refill ground-water reserves. Where there are no (35) , the rains run in sheets of water off the land, (36) the soil with them. Land (37) with trees and other plants (38) 20 times more rainwater than (39) earth. As they grow, trees absorb carbon dioxide, the main (40) of the "greenhouse effect" , which (41) irreversibly to change the world’s climate. Together, the world’s trees, plants and soils contain three times as much carbon as (42) is in the atmosphere. The world’s forests (43) the vast majority of its animal and plant species. The tropical rainforests (44) have well over half of them, (45) they cover only about 6% of the Earth’s land surface.

A. bind
B. require
C. give
D. offer