题目

— You didn’t tell me the truth about this matter, Barbara．    — Are you _____ me of lying?        A．charging   B．reminding C．catching    D．accusing 答案：D用数学归纳法证明：对于一切n∈N*，都有(12+1)+(22+2)+…+(n2+n)=n(n+1)(n+2)3．