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Ａ 组 选择题(在每小题给出的四个选项中,只有一项是符合题目要求的,请将正确选项的代号填在题后的括号内)1 Ｃ2ｎ+2Ｃｎ-1ｎ+Ｃｎ-2ｎ等于( )(Ａ)ｎ2+ｎ. (Ｂ)ｎ2+ｎ2.(Ｃ)2(ｎ2+ｎ).(Ｄ)ｎ2+3ｎ+2.2 四名学生争夺三项比赛冠军,获得冠军的所有可能情形有(
Group A multiple-choice questions (only one of the four options given in each question is subject to the requirements of the title, please fill in the parentheses after the question with the correct option) 1 C2n+2Cn-1n+Cn-2n Equal to ()(A)n2+n. (B)n2+n2.(C)2(n2+n).(D)n2+3n+2.2 Four students compete for three championships and all possible scenarios for winning the championship Have(