A:氯、溴、碘
B:钠、镁、铝
C:烧碱、氢气
D:食盐、淡水
The young man named Mario____ ____ ____ ____the supermarket.
已知集合A={a,2},集合B={a+1,5},若A∩B={2},则A∪B=( )
宋太祖在位期间,为加强中央集权,采取了哪些措施?