设<img src="/lqwvjeImg/8e/8e41caf6b38375886e1aa2532cca6a47.png">和<img src="/lqwvjeImg/40/40545a24a954ba42f36bb986e7196505.png">都是非空集合,而<img src="/lqwvjeImg/9b/9b5ebbba4da1729b64370b459e873c27.png">是<img src="/lqwvjeImg/df/df46b8004f9ad642e924373f2cf49a70.png">到<img src="/lqwvjeImg/40/40545a24a954ba42f36bb986e7196505.png">的一个映射,那么( )<br>·集合<img src="/lqwvjeImg/0f/0f6e4f66f95e27c60dd5cad87abda6eb.png">中两两都不相同;<br>·<img src="/lqwvjeImg/8e/8e41caf6b38375886e1aa2532cca6a47.png">的次序不能调换;<br>·<img src="/lqwvjeImg/df/df46b8004f9ad642e924373f2cf49a70.png">中不同的元对应的象必不相同;<br>·一个元<img src="/lqwvjeImg/07/079dbd4688a3f3e09f17fdda0e79df48.png">的象可以不唯一。