A new study from Switzerland sheds light on where ice sheets melted during the ice age. It now seems that the ice melted at both ends of the earth, rather than just in ei-ther northern or southern regions.
This surprised the researchers from the University of Bern. Scientists have long assumed that most of the ice that melted was in the Northern hemisphere (半球) during the 30,000-year long ice age. That belief was held because the North Pole is surrounded by land, while the South Pole is surrounded by the Antarctic Ocean. It is easier for ice sheets to grow on land. If surrounded by sea the ice can easily just slip into the ocean instead of building up.
The researchers used a computer model to look at ways the ice could melt and how it might affect sea levels. They compared these results to evidence of how temperatures and currents actually changed during that time. The model showed that if it was only in the Northern hemisphere that ice melted, there would have been a bigger impact (影响) on ocean currents (洋流) and sea temperatures than what actually happened. Studies suggest that melting just in the Southern hemisphere would have been impossible, too. The only reasonable conclusion, the scientists could make, was that ice melted equally in the North and the South.
It is still a mystery as to what caused the temperature changes that caused the ice to melt.
The North Pole is surrounded by land, while the South Pole is surrounded by the Antarctic Ocean. So scientists thought that ______.
A.most of the ice melted in the Northern hemisphere
B.most of the ice melted in the Southern hemisphere
C.The North Pole is colder than the South Pole
D.The South Pole is colder than the North Pole
第4题
A.对准源皮距后升床到肿瘤中心高度
B.先对好源皮距再给大机架角度
C.只需前野对源皮距,对准中十字线按医嘱给后两野角度不需要再对距离
D.先对好机架角再对好源皮距
E.以上全不对
第7题
A.按医嘱要求线对准距离,再给角度
B.按医嘱要求线给角度,再对距离
C.为满足照射灯光野与皮肤野吻合,机架角度可以变化
D.源皮距一定要准确
E.准直器角度固定不变
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