D. It is a new kind of free online course of Harvard and MIT.

E

Plants are flowering faster than scientists predicted（预测）in reaction to climate change,

which could have long damaging effects on food chains and ecosystems.

Global warming is having a great effect on hundreds of plant and animal species around the

world, changing some living patterns, scientists say.

Increased carbon dioxide（CO2）how plants produce oxygen, while higher temperatures and changeable can

change their patterns of growth.

―Predicting species‘ reaction to climate change is a major challenge ‖ said the

researches of several U.S. universities. The study, published on the Nature website, the plant life cycle studies

and experiments across four continents and that some experiments had

underestimated（低估） ―Across all species, the experiments the speed of the advance — for both

leafing and flowering — ‖ the study said.

react to climate change, it said.

Plants are for life on the Earth. They are the base of the food chain, using

to produce sugar from carbon dioxide and water. They let out oxygen

‘s average temperature has risen by about 0.8℃ since 1900, and

℃ every ten years since 1979.

So far, efforts to cut emissions（排放）of planet-warming greenhouse gases are not seen as

enough to prevent the Earth heating up beyond 2℃ this century — a point scientists say will

bring the danger of a changeable climate in which weather extremes are common, leading to

drought, floods, crop failures and rising sea levels.

57. What is the key information the author wants to give in Paragraph 1?