题目

There are some health problems that, whenin time, can become bigger ones later on. A . not treated B . not being treated C . not to be treated D . not having been treated 答案：A 已知集合A＝{1，2，3，…，10}，B＝{1，，，…，}，设x∈A，y∈B，试给出一个对应法则f使f：A→B是从集合A到集合B的映射f：x→y＝________．