【单选题】已知集合A='{1,' 2, 3, 4},函数f(x)的定义域、值域都是A,且对于任意 , ,设 1 , 2 , 3 , 4 是1,2,3,4的任意一个排列,定义数表 ,若两个数表的对应位置上至少有一个数不同,就说这是两张不同的数表,那么满足条件的不同的数表的张数为( )
【单选题】What is one of the 4 great inventions of modern China?
【判断题】( )在中性点接地供电系统中,I类工具应采取保护接地。
【简答题】Todays policemen in large cities throughout the world rely on modern inventions to help them in their work. In most places motor scooters and police patrol cars have done away with the need to patrol ...
【多选题】发音器官包括三大部分:A. 、B. 、C 。
【单选题】设A、B为任意集合,|A|=m,|B|=n,则从A到B的关系有( )个。
【单选题】People living in modern times benefit from many discoveries and inventions that have _________the world.
【判断题】若关系R设A、B为任意的2个集合,则A×B=B×A 。