2015年职称英语理工类A级考试真题阅读判断.docVIP

2015年职称英语理工类A级考试真题：阅读判断 下面的短文后列出了7个句子，请根据短文的内容对每个句子做出判断：如果该句提供的是正确信息，请选择A；如果该句提供的是错误信息，请选择B；如果该句的信息文中没有提及，请选择C。 Lack of Oxygen Delayed the Rise of Animals on Earth Scientists have long speculated as to why animal species didnt flourish sooner,once sufficient oxygen covered the Earths surface.Animals began to prosper at the end of the Proterozoic period,about 800 million years ago — but what about the billion-year stretch before that,when most researchers think there also was plenty of oxygen? Well,it seems the air wasnt so great then,after all. In a study published Oct.31 in Science,Yale researcher Noah Planavsky and his colleagues found that oxygen levels during theboring billionperiod were only 0.1% of what they are today.In other words,Earths atmosphere couldnt have supported a diversity of creatures,no matter what genetic advancements were poised to occur. There is no question that genetic and ecological innovation must ultimately be behind the rise of animals,but it is equally unavoidable that animals need a certain level of oxygen,said Planavsky,co-lead author of the research along with Christopher Reinhard of the Georgia Institute of Technology.Were providing the first evidence that oxygen levels were low enough during this period to potentially prevent the rise of animals. The scientists found their evidence by analyzing chromium (Cr) isotopes in ancient sediments from China,Australia,Canada,and the United States.Chromium is found in the Earths continental crust,and chromium oxidation is directly linked to the presence of free oxygen in the atmosphere. Specifically,the team studied samples deposited in shallow,iron-rich ocean areas,near the shore.They compared their data with other samples taken from younger locales known to have higher levels of oxygen. Oxygens role in controlling the first appearance of animals has long vexed scientists.We were missing the right approach until now,Planavsky said.Chromium gave us the proxy.Previous estimates put the