题目

若复数(1+bi)(2+i)是纯虚数(i是虚数单位，b是实数)，则b=（     ）   (A) -2     （B）     (C)     (D)2 答案：DGreat attention must ______ education, especially in the countryside.A．pay to developB．be paid to developC．pay to developingD．be paid to developing