题目

______, We were taken to see the library.  A. We had been shown the classrooms       B. Being shown the classrooms  C. Having been shown the classrooms        D. Having shown the classroom 答案：C下列结论正确的是（ ）A．?x∈R，使2x2-x+1＜0成立B．?x＞0，都有成立C．函数的最小值为2D．0＜x≤2时，函数y=x-有最大值为