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【单选题】为了求1+2+22+…+22009的值，可令s=1+2+22+…+22009，则2s=2+22+23+24+…+22010，因此2s﹣s=22010﹣1，所以1+2+22+…+22009=22010﹣1，仿照以上推理计算出1+7+72+73+…72010的值 [ ]
A.
72010﹣1
B.
72011﹣1
C.
D.
【单选题】The three main types of secondary education in the United States have been provided by the Latin grammar school, the academy, and the public high school. The first of these was a colonial institution....
A.
European educational systems are not good
B.
as high schools developed in the United States, the decision was made to make them responsible to people from all classes of society
C.
there was an aristocratic and selective principle in the European educational tradition
D.
public high schools in the United States embraced the European educational tradition