单射在满足什么条件时是满射?() ["两集合元素个数相等","两集交集为空集","两集合交集不为空集","两集合元素不相等"]
Zm1*Zm2的笛卡尔积被称作是Zm1和Zm2的什么?() ["算术积","集合","直和","平方积"]
中线测量的主要任务是通过直线和曲线的测设,将路线中心线的平面位置具体地标定在现场上,并测定路线的实际里程。
具有感染性的,比较平稳而相对持久的情绪状态是() ["A.热情 ","B.心境 ","C.激情 ","D.应激"]
(x2-1)2在复数域上中有几个根?() ["1.0","2.0","3.0","4.0"]
从激素分布和营养学理论,简述茶树生长和休止关系