类内初始化成员问题

#include<iostream>
using namespace std;
class Student{
    private:
        string s[3];
    public:
        Student()
        {
            cout<<"use one"<<endl;
        }
        Student(string a,string b,string c)
        {
            s[0] = a;
            s[1] = b;
            s[2] = c;
            cout<<"use two"<<endl;
        }
        
};
int main()
{
    Student s1("123","1234","12345");
    Student s2();
    return 0;
}
帮忙看一下，为什么会跳过对象s2直接结束。