[填空题]Tropical rainforests comprise only 40% of the world’s tropical forests and only 20% of the world’s total forests.

[填空题]Tropical rainforests comprise only 40% of the world’s tropical forests and only 20% of the world’s total forests.

[单项选择]Passage Six

Rainforests

Tropical rainforests are the most diverse ecosystem on Earth, and also the oldest. Today, tropical rainforests cover only 6 percent of the Earth’s ground surface, but they are home to over half of the planet’s plant and animal species. In this completely unique world, there are thousands of species we have yet to discover.
In this article, we’ll travel into the tropical rainforest to see what makes it such a beautiful environment for plants and animals. We’ll also see why the rainforests are in danger and look at some of the ways this affects us.
What Is a Rainforest
Generally speaking, a rainforest is an environment that receives high rainfall and is dominated by tall trees. A wide range of ecosystems fall into this category, of course, including the old-growth temperate forests of the Pacific Northwest. But most of the time when people talk about rainforests, they m
A. we are familiar with them
B. no more species of rainforests need to be discovered
C. most species will not survive without tropical rainforests on Earth
D. tropical rainforests are the oldest and the most diverse ecosystem

[简答题]

The world’s tropical rainforests comprise some 6% of the Earth’s land area and contain more than half of all known life forms, or a conservative estimate of about 30 million species of plants and animals. 61)Some experts estimate there could be two or even three times as many species hidden within these complex and fast- disappearing ecosystems — scientists will probably never know for certain so vast is the amount of study required Time is running out for biological research. 62)Commercial development is responsible for the loss of about 17 million hectares of virgin rainforest each year — a figure approximating 1% of what remains of the world’s rainforests.
The current devastation of once impenetrable rainforest is of particular concern because, although new tree growth may in time repopulate felled areas, the biologically diverse storehouse of flora and fauna is gone forever. 63)Losing this bountiful inheritance, which too