托福阅读否定事实信息题范例7

　　无明确定位词：

　　例题7：

　　Paragraph 4 Dissatisfaction with conventional explanations for dinosaur extinctions led to a surprising observation that, in turn, has suggested a new hypothesis. Many plants and animals disappear abruptly from the fossil record as one moves from layers of rock documenting the end of the Cretaceous up into rocks representing the beginning of the Cenozoic (the era after the Mesozoic). Between the last layer of Cretaceous rock and the first layer of Cenozoic rock, there is often a thin layer of clay. Scientists felt that they could get an idea of how long the extinctions took by determining how long it took to deposit this one centimeter of clay and they thought they could determine the time it took to deposit the clay by determining the amount of the element iridium (lr) it contained.

　　In paragraph 4, all the following questions are answered EXCEPT:

　　Why is there a layer of clay between the rocks of the Cretaceous and Cenozoic?

　　Why were scientists interested in determining how long it took to deposit the layer of clay at the end of the Cretaceous?

　　What was the effect of the surprising observation scientists made?

　　Why did scientists want more information about the dinosaur extinctions at the end of the Cretaceous?