题目

矩形线圈在匀强磁场中，绕垂直磁场方向的轴匀速转动时，线圈平面跟中性面重合的瞬间，下面的说法中正确的是（） A . 线圈中的磁通量为零 B . 线圈中的感应电动势最大 C . 线圈的每一边都不切割磁感线 D . 线圈所受的磁场力不为零 答案：CFew politicians have been as respected in life or honoured in death as former South African President Nelson Mandela. Since the anti-apartheid (反对种族隔离)hero and South Africa's first black president died at 95 in his Johannesburg home on Dec. 5， people around the world, no matter how different their backgrounds and political beliefs are, have been memorializing him in different languages and in different ways.Mandela was not perfect, and the country he leaves behind still faces many problems. But despite his short?comings ,he leaves the world a heritage to treasure, said a Beijing News editorial on Saturday.At one time,South Africawas the crudest corner of the world, having serious apartheid. At that time black and white people's living an equal life in the coun?try was an unachievable dream. Both the introduction of democracy(民主)and the avoidance of what would have in all likelihood been Africa's bloodiest civil war were regarded as missions impossible.It was Mandela who led South Africans to put an end to apartheid, realize social harmony and build a dream nation. There may still be disagreements from time to time, but people seek to resolve their problems and differences through civilized means.This is the most valuable heritage of Mandela, who endured 27 years of hardships in prison and walked out with new reflections and thoughts with which to guide all races to own their equal rights and interests. His perseverance and tolerance won him supporters both at home and abroad and moved even his enemies.The reason why South Africa has realized a stable change and avoided hatred and killing between different races is the establishment of a foundation of mutual trust and recognition of the need for social order, rhe co-existence of different human races under the principle of equality and their resorting to peaceful, democratic and legal means to resolve differences are part of Mandela's memorable contribution.Since 1999, Mandela lived a quiet and retired life. He resigned at the peak of his political life and avoided repeating the mistakes of many political figures of his time. He performed a politician's mission in an almost perfect way.1. What can we know about the situation from the un?derlined sentence in the third paragraph?A.It seemed difficult to realize democracy and avoid the civil war at that time.B.Democracy could not be realized unless peoplewon the civil war.C.The bloodiest civil war prevented the introduction of democracy toSouth Africa.D.The introduction of democracy avoided the civil war inSouth Africa.2.Which of the following about Mandela's contribution to his country is NOT true?A.Mandela led his people to put an end to apartheid.B.Mandela inspired his people to deal with problems and differences in civilized ways.C.Mandela taught his people to realize the impor?tance of social order.D.Mandela created a dream nation for his people without any disagreements.3.According to the last paragraph, the writer's attitude towards Mandela's retirement is .A. critical   B. supportiveC. indifferent  D. doubtful4.What words can best describe Nelson Mandela ac?cording to the passage?A.Quiet and wise.B.Hard-working and wealthy.C.Perseverant and selfless.D.Brave and aggressive.