题目

. _______of the household rubbish _______recycled or reused since the new technology was applied. A．Three-fourth; has                                       B．Three-fourth; have been C．Three-fourths; has been                             D．Three-fourths; have 答案：C展开式中不含x4项的系数的和为（ ）A．-1B．0C．1D．2