【简答题】设有X={a,b,c}上关系R 1 ,R 2 ,R 3 ,R 4 为: (1)R 1 ={(a,b),(a,c),(c,b)}; (2)R 2 ={(a,b),(b,c),(c,c)}; (3)R 3 ={(a,b),(b,a)(c,c)}; (4)R 4 ={(a,b),(b,c)(c,a)}. 求它们的传递闭包:t(R 1 ),t(R 2 ),t(R 3 ),t(R 4 ).
【简答题】A.Took balanced meals with champagne. B.Ate vegetables and fruit only. C.Refrained from fish or meat. D.Avoided eating rich food.
【判断题】One mother refrained from posting her son's photos online when she considered the matter from her son's perspective. (10.0分)A. √ B. ╳
【单选题】下列选项中不属于快递业发展“十三五”规划基本思路的是( )。
【简答题】设有X={a,b,c)上关系:R 1 ,R 2 ,R 3 ,R 4 为: (1)R 1 ={(a,b),(a,c),(c,b)); (2)R 2 ={(a,b),(b,c),(c,c)}; (3)R 3 ={(a,b),(b,a),(c,c)}; (4)R 4 ={(a,b),(b,c),(c,a)}. 求它们的传递闭包:t(R 1 ),t(R 2 ),t(R 3 ),t(R 4 ).
【多选题】根据系统和环境的联系方式可将系统划分( )