Thanks For Helping.

#include <bits/stdc++.h>

using namespace std;

//=================================================STRUCTURES===============================================

struct DateTime
{
    struct Date
    {
        int day,month,year;

    } date;

    struct Time
    {
        int hour,min;

    } time;
};

struct Note
{
    string FacultyName;

    int LevelOfStrictness;

    string Others;
};

struct subject
{
    struct DateTime StartTime,EndTime;

    string ClassName,ClassType;

    int ThresholdPercentage,MaxPossiblePercentage;

    struct Note notes;

};

struct students
{
    struct subject *subjects;

    string name;

    int MaxSubjects;

} *student;

//==============================================FUNCTIONS==================================================

void PrintStudentSubjects(int x)
{
    int i,n;

    n=student[x].MaxSubjects;

    for(i=1;i<=n;i++)
    cout<<student[x].subjects[i].ClassName<<'\n';
}

//================================================MAIN=====================================================

int main(void)
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int NStudents,Subjects,i,j;

    cout<<"Enter Number of Students:- ";

    cin>>NStudents;

    student=(struct students*)malloc(sizeof(struct students)*(NStudents+1));

    cout<<'\n';

    for(i=1;i<=NStudents;i++)
    {
        cout<<"Enter Number of Subjects for "<<i<<" Student:- ";

        cin>>Subjects;

        student[i].MaxSubjects=Subjects;

        student[i].subjects=(struct subject*)malloc(sizeof(struct subject)*(Subjects+1));

        cout<<'\n';

        for(j=1;j<=Subjects;j++)
        {
            cout<<"Enter the name of Subject "<<j<<" :- ";

            cin>>student[i].subjects[j].ClassName;                // <<<<==================Fault Here.
        }

        PrintStudentSubjects(i);
    }

    return 0;
}