A rainforest is an area ____ (cover) by tall trees with the total high rainfall spreading quite equally through the year. Rainforests have a great effect on the world environment because they can take in heat from the sun and adjust the climate.____the forest cover, these areas would reflect more heat into the atmosphere,____ (warm) the rest of the world. Losing the rainforests may also influence wind and rainfall patterns, potentially causing certain natural disasters all over the world.

    In the past hundred years, humans ____ (begin) destroying rainforests in search of three major resources: land for crops, wood for paper and other products, land for raising farm ____ (animal). This action affects the environment as a whole. For example, a lot of carbon dioxide in the air comes from burning the rainforests. People____ (obvious) have a need for the resources we gain from cutting trees____ we will suffer much more than we will benefit.

    Rainforests are often called the world's drug store. More than 25% of the medicines we use today come from plants in rainforests. However, fewer than 1% of rainforest plants have been examined for their____ (medicine) value. It is extremely likely ____ our best chance to cure diseases____ (lie) somewhere in the world's shrinking rainforests.

参考公式： $K^2=\frac{n{\left(ad-bc\right)}^2}{\left(a+b\right)\left(c+d\right)\left(a+c\right)\left(b+d\right)}$ ，其中 $n=a+b+c+d$ ．

参考临界值：