C
Walk through the Amazon rainforest today and you will find it is steamy ,warm ,damp and thick .But if you had been 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 like the Amazon might have reacted（反应）to the cold ,dry climates of the ice ages ,but until now ,no one has reached a satisfying answer.
Rainforests like the Amazon are important for mopping up CO2 from the atmosphere and helping to slow global warming . Currently the trees in the Amazon take in around 500 million tonnes of CO2 each year; equal to the total amount of CO2 giving off in the UK each year. But how will the Amazon react to future climate change? If it gets drier ,will it still survive and continue to draw down CO2 ?Scientists hope that they will be able to learn in advance how the rainforest will manage in the future by understanding how rainforests reacted to climate change in the past.
Unfortunately ,getting into the Amazon rainforest and collecting information are very difficult .To study past climate ,scientists need to look at fossilized pollen ,kept in lake muds .Going back to the last ice age means drilling deep 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 ares 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 rainforest reacts to climate change.
【題組】67．The best title for this passage may probably be .
(A)Studies of the Amazon (B)Climates of the Amazon
(C)Secrets of the Rainforests (D)Changes of the Rainforests
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