Walk through the Amazon rainforest today and you will find it steamy, warm, damp and thick. But if you had been there around 15,000 years ago, during the last ice age, would it have been the same? For more than 30 years, scientists have been arguing about how rainforests might have reacted to the cold, dry climate of the ice ages, but till now, no one has reached a satisfying answer.
Rainforests like the Amazon are important for mopping up CO2 from the atmosphere and helping tosolve global warming. Currently the trees in the Amazon take in around 500 million tons of CO2 each year: equal to the total amount of CO2 given off in the UK each year. But how will the Amazon react to the future climate change? If it gets drier, will it survive and continue to draw down CO2? Scientists hope that they will be able to learn in advance how the rainforest will managein the future by understanding how rainforests reacted to climate change in the past.
Unfortunately, collecting information is incredibly difficult. To study the past climate, scientists need to look at fossilized pollen（花粉）kept in lake mud, Going back to the last ice age means drilling down into lake sediments（沉淀物）, which requires specialized equipment and heavy machinery. There are very few roads and paths, or places to land helicopters and aeroplanes. Rivers tend to be the easiest way to enter the forest, but this still leaves vast areas between the rivers completely unsampled（未取样）. So far, only a handful of cores have been drilled that go back to the last ice age and none of them provide enough information to prove how the Amazon forest reacts to climate change.
32.How do scientists study the past climate change?
A. By predicting the climate change in the future.
B. By drilling down deep into land sediments.
C. By analyzing fossilized pollen in lake mud.
D. By taking samples from rivers in the Amazon.
33.Why is it difficult to collect information about the past climate change?
A. Because scientists can't find proper equipment and machinery.
B. Because it is very difficult to obtain complete samples.
C. Because helicopters and aeroplanes have no place to land.
D. Because none of the cores provide any information.
34.Where is the passage most probably taken from?
A. A medical journal. B. A news report
C. A travel brochure. D. A science magazine.
35.The best title for the text may be .
A. Secrets of the Rainforest
B. Climates of the Amazon
C. The History of the Rainforest
D. Changes of the Rainforest