题目

如图，等边三角形ABC的边长为2，过点B的直线⊥AB，且△ABC与△A′BC′关于直线对称，D为线段BC′上一动点，则AD + CD的最小值是      A．4    B．    C．    D．     答案：AThe students are doing _______ important task; they share _____ common goal , that is, to be admitted into the famous universities. A．an, a             B．an, the            C．不填， 不填       D．不填 , a