72. A rainforest is an area covered by tall trees with thetotal high rainfall spreading quite equally through theyear and the temperature rarely dipping below l6℃.Rainforests have a great effect on the worldenvironment because they can take in heat from thesun and adjust the climate. Without the forestcover，these areas would reflect more heat into theatmosphere，warming the rest of the world. Losingthe rainforests may also influence wind and rainfallpatterns，potentially causing certain naturaldisasters all over the world.
In the past hundred years，humans have begun destroying rainforests in search of three majorresources(资源)：land for crops，wood for paper and other products，land for raising farmanimals. This action affects the environment as a whole. For example，a lot of carbon dioxide(二氧化碳)in the air comes from burning the rainforests. People obviously have a need for theresources we gain from cutting trees but we will suffer much more than we will benefit.
There are two main reasons for this. Firstly，when people cut down trees，generally they canonly use the land for a year or two. Secondly，cutting large sections of rainforests may providea good supply of wood right now，but in the long run it actually reduces the world’s woodsupply.
Rainforests are often called the world’s drug store. More than 25％ of the medicines we usetoday come from plants in rainforests. However，fewer than l％of rainforest plants have beenexamined for their medical value. It is extremely likely that our best chance to cure diseases liessomewhere in the world’s shrinking rainforests.
Rainforests can help to adjust the climate because they ________.
(A). reflect more heat into the atmosphere
(B). bring about high rainfall throughout the world
(C). rarely cause the temperature to drop lower than l6℃
(D). reduce the effect of heat from the sun on the earth
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