2．已知集合U={1,2,3,4,5,6,7},A={2,3,4,5},B={2,3,6,7},则|2019年河北高考文数答案和在线做题

2．已知集合U={1,2,3,4,5,6,7},A={2,3,4,5},B={2,3,6,7},则

（D）{1,6,7}