简答题(共3小题；每小题2分，满分6分) 阅读下面短文，根据第73至第75小题的具体要求，简要回答问题。 The north magnetic pole(磁极)is no longer a resident of Canada.It has drifted across the Canadian Arctic and is now angling toward Siberia. Not to be confused with the geographic North Pole—the northern extremity of the Earth’s axis(地轴),the north magnetic pole(where the Earth’s magnetic field is directed downward)is moving due to natural changes in the Earth’s magnetic field,a process that originates about 3000 kilometers below our feet,in the outer core(核心)of the planet.But scientists are now noticing that the magnetic pole has picked up its pace. Over the past century,the pole has been migrating at an average speed of about 10 kilometers per year,says Larry Newitt,head of Geomagnetic Laboratory at Natural Resources Canada in Ottawa.Since the 1970s,this speed has increased to about 50 kilometers per year. Scientists are wondering why the speed is increasing,says Newitt.One hypothesis(假说)relates it to “magnetic jerks”,sudden shifts(变化)in the rate of change of the magnetic field.There have been three jerks in the past four decades,each one correlating to an increases in speed. If the north magnetic pole continues at its current rate,it could reach Siberia by 2056. “For most of recorded history,the pole has been a part of Canada,and now it’s not,”says Newitt.“It may be a blow to our collective psyche,but other than that,it doesn’t have a major effect on most people’s existence.” 73.Find in the passage a word closest in meaning to the underlined word “angling”. ____________________________________________________________ 74.What could happen to the north magnetic pole by the middle of the 21st century?(回答词数不超过8个) ____________________________________________________________ 75.What is the main idea of the passage?(回答词数不超过8个) ____________________________________________________________