题目

设集合A={x|x≥–3}，B={x|–3<x<1}，则A∪B=( )A.{x|x>–3} B.{x|x<1}C.{x|x≥–3} D.{x|–3≤x<1} 答案：【答案】C【解析】根据并集的运算律可计算出集合.，，由并集的运算律可得，故选：C.20、About 90 percent of the equipment presented by the administration, as well as the facilities of our own, _______ made good use of in the teaching. A．have               B．has          C．have been               D．has been