题目内容：

Around the world coral reefs(珊瑚礁) are facing threats(威胁) brought by climate change and great changes in sea temperatures. While ocean warming has been the primary focus for scientists and ocean policy managers, cold events can also whiten corals. A new study by scientists compared damaged to corals exposed to heat as well as cold stress. The results show that cool temperatures can cause more damage in the short term, but heat is more destructive(破坏性的) in the long run.

Climate change is widely known to produce warming conditions in the oceans, but extreme cold-water events have become more frequent and serious as well. In 2010, for example, coral reefs around the world faced on of the coldest winters and one of the hottest summers on record.

During a unique experiment, corals under cold temperatures suffered greater damage in just days compared with heat treated corals. Yet the researchers found that corals were eventually able to adjust to the cold conditions, make their health stable and continue to grow. However, over the long term corals subjected to heat suffered more greatly than those in cold, with evidence of severe whitening and growth stoppage, which leads to death.

The coral’s ability to adjust to cool temperatures surprised the researchers, who say the study’s results show the complexities(复杂性) of monitoring coral health in response to different environmental factors(因素).

“Global warming is associated with increases but also decreases of temperatures,” said Deheyn, one of the researchers. “Not much has been known about the comparative effects of temperature decrease on corals. These results are important because they show that corals react differently to temperature differences, which is important for future management of coral reefs in the field of climate change.”

1.Which of the following is TRUE according to the passage?
A. Corals are unable to adjust to temperature changes.
B. Cold temperature causes greater damage to corals.
C. Hot temperature helps coral reefs to grow quickly.
D. Heat and cold damage corals in their own ways.

2.We can learn from the passage that         .
A. scientists used to pay no attention to the effect of cold events on corals
B. 2010 witnessed one of the greatest temperature differences on record
C. corals prefer warmer conditions to cold temperatures in the long run
D. global warming has nothing to do with the decrease of temperature

3.According to the research,            .
A. corals may continue to grow in cold events after a few days
B. cold events help corals grow more quickly in a short time
C. corals show no response to hot temperatures in the first days
D. corals are whitened mainly because of warm temperatures

4.Scientists reached the conclusion through              .

A. news report              B. scientific study              C. great imaginationD.natural conditions