54. What is said about online education in the text?
A. Universities have been trying online courses.
B. About 2,000 online courses have been offered.
C. Over 100 million people have finished courses online.
D. Stanford and Yale together have courses similar to edX.
55. The underlined part in the text probably means “         ”.
A. Get ready for the difficulties
B. Get ready for this educational change
C. Get prepared to complete the online courses
D. Get prepared to make materials for the edX courses
56. What can be said about MITx according to the text?
A. It is first offered as part of the edX learning program.
B. It is another free MIT-Harvard online learning program.
C. It is a standard to recognize online learners’ achievement.
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）in the air from burning coal and oil can have an effect on how plants produce oxygen, while higher temperatures and changeable rainfall patterns can change their patterns of growth.
    “Predicting species’ reaction to climate change is a major challenge in ecology,” said the researches of several U.S. universities. They said plants had been the key object of study because their reaction to climate change could have an effect on food chains and ecosystem services.
    The study, published on the Nature website, uses the findings from plant life cycle studies and experiments across four continents and 1,634 species. It found that some experiments had underestimated（低估）the speed of flowering by 8.5 times and leafing by 4 times.
    “Across all species, the experiments under-predicted the speed of the advance — for both leafing and flowering — that results from temperature increases,” the study said.
    The design of future experiments may need to be improved to better predict how plants will react to climate change, it said.
    Plants are necessary for life on the Earth. They are the base of the food chain, using photosynthesis（光合作用）to produce sugar from carbon dioxide and water. They let out oxygen which is needed by nearly every organism on the planet.
    Scientists believe the world’s average temperature has risen by about 0.8℃ since 1900, and nearly 0.2℃ 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?
A. Plants’ reaction to weather could have damaging effects on ecosystem.
B. The increasing speed of flowering is beyond scientists’ expectation.
C. Climate change leads to the change of food production patterns.
D. Food chains have been seriously damaged because of weather.

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