单项选择题
Why doesn't the algorithm need to call remove() to delete an element? 为什么该算法中不需要调用remove()进行元素删除？
A．There is no duplicate element 本来就没有重复元素
B．Duplicate elements are ignored directly 重复元素被直接忽略了
C．Duplicate elements are moved to the end of the vector 重复元素被移到了向量末尾
D．Duplicate elements have been modified to be non-repeating elements 重复元素修改成了不重复的元素
