课时同步练习(四) 并集与交集(建议用时:60分钟)[合格基础练]一、选择题1.设集合A={1,2,3},B={2,3,4},则A∪B=( )A.{1,2,3,4} B.{1,2,3}C.{2,3,4}D.{1,3,4}A [∵A={1,2,3},B={2,3,4},∴A∪B={1,2,3,4}.故选A.]2.已知集合A={1,2,3,4},B={2,4,6,8},则A∩B中元素的个数为( )A.1 B.2C.3 D.4B [∵A={1,2,3,4},B={2,4,6,8},∴A∩B={2,4}.∴A∩B中元素的个数为2.故选B.]3.已知集合A={x|x+1