Эта ошибка у меня уже второй раз, почему она возникает и как это исправить?

У меня эта ошибка уже второй раз, в прошлый раз я ее исправил с помощью этой строки:"test.push_back(Test{});". Я не очень понимаю, что значит эта строка, но он помог в прошлый раз. Вот сама ошибка и мой код(ошибка в case4 скорее всего из за етих строк:"cin >> test[choose].student[num_of_student].name;", "test[choose].student[num_of_student].mark = right;"):

 #include <iostream>
#include <vector>
#include <string>

using namespace std;


int num_of_test = 0;
int choose = 0;
int num_of_student = 0;

struct Information
{
    int mark;
    string name;
};
struct Question
{
    string question;
    string var_answers[3];
    string answer;
    //vector<int> mark;
    //vector<string> name;


    bool check_answer(string num)
    {
        if (answer == num)
            return true;
        return false;
    }
};
class Test
{

public:
    vector <Question> questions;
    vector <Information> student;
};

int main()
{
    setlocale(LC_ALL, "");
    int password = 0;
    int count_of_questions = 0;

    vector <Test> test;
    test.push_back(Test{});

    while (true)
    {
        cout << "select operation which you want to do" << endl;
        cout << "1 - create new test" << endl;
        cout << "2 - edit test" << endl;
        cout << "3 - delete test" << endl;
        cout << "4 - pass the test" << endl;
        cout << "5 - show all tests" << endl;
        cout << "6 - show all students" << endl;
        cout << "7 - log uot" << endl;
        int select;
        cin >> select;

        switch (select)
        {
        case 1: {//створення тесту
            cout << "Input password";
            cin >> password;
            if (password == 1)
            {
                cout << "How many questions do you want to ask?" << endl;
                cin >> count_of_questions;
                test[num_of_test].questions.resize(count_of_questions);//виділення пам'яті під вказану к-сть питань
                for (size_t i = 0; i < count_of_questions; i++)
                {
                    test.push_back(Test{});
                    cout << "Write a question:" << endl;
                    cin >> test[num_of_test].questions[i].question; //в якийст тест добавляється питанння
                    cout << "Enter 1-st variaty of answer:" << endl;//варыанти відповідей в цьому питаннні-----
                    cin >> test[num_of_test].questions[i].var_answers[0];
                    cout << "Enter 2-nd variaty of answer:" << endl;
                    cin >> test[num_of_test].questions[i].var_answers[1];
                    cout << "Enter 3-rd variaty of answer:" << endl;
                    cin >> test[num_of_test].questions[i].var_answers[2];//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                    cout << "Enter correct answer" << endl;
                    cin >> test[num_of_test].questions[i].answer;//правильна відповідь
                }
                num_of_test++;
            }
            else
                cout << "Error";
            break; }

        case 2: { //редагування тесту
            cout << "Input password";
            cin >> password;
            if (password == 1)
            {
                cout << "Enter num of test" << endl;
                cin >> choose;

                cout << "Enter num of question which you want to change" << endl;
                int num_change;
                cin >> num_change;
                cout << "Write a new question:" << endl;
                cin >> test[choose].questions.at(num_change).question;
                cout << "Enter 1-st variaty of answer:" << endl;
                cin >> test[choose].questions.at(num_change).var_answers[0];
                cout << "Enter 2-nd variaty of answer:" << endl;
                cin >> test[choose].questions.at(num_change).var_answers[1];
                cout << "Enter 3-rd variaty of answer:" << endl;
                cin >> test[choose].questions.at(num_change).var_answers[2];
                cout << "Enter correct answer" << endl;
                cin >> test[choose].questions.at(num_change).answer;
            }
            else
                cout << "Error";
            break; }

        case 3: {//видалення тесту
            cout << "Input password";
            cin >> password;
            if (password == 1)
            {
                vector <Test>::iterator i = test.begin();
                cout << "Enter num of test to delete: " << endl;
                int num;
                cin >> num;
                advance(i, num);
                test.erase(i);
            }
            else
                cout << "Error";
            break; }

        case 4: {//здача тесту

            cout << "Enter num of test" << endl;
            cin >> choose;
            cout << "Enter your name" << endl;
            
            cin >> test[choose].student[num_of_student].name;
            
            int right = 0;
            int wrong = 0;
            for (int i = 0; i < count_of_questions; ++i)
            {
                cout << endl;
                cout << test[choose].questions[i].question << endl;
                cout << test[choose].questions[i].var_answers[0] << endl;
                cout << test[choose].questions[i].var_answers[1] << endl;
                cout << test[choose].questions[i].var_answers[2] << endl;
                string ans;
                cin >> ans;
                if (test[choose].questions[i].check_answer(ans))
                    right++;
                else
                    wrong++;
            }
            cout << "\nCorrect answers - " << right;
            cout << "\nUncorrect answers - " << wrong << endl;
            test[choose].student[num_of_student].mark = right;

            break; }
        case 5: { //показ всіх питань
            cout << "Input password";
            cin >> password;
            if (password == 1)
            {
                for (size_t j = 0; j < test.size() - 1; j++)
                {
                    cout << "________________________________________________" << endl;
                    for (size_t i = 0; i < count_of_questions; i++)
                    {
                        cout << "Question: - " << test[j].questions[i].question << endl;
                        cout << "1)" << test[j].questions[i].var_answers[0] << endl;
                        cout << "2)" << test[j].questions[i].var_answers[1] << endl;
                        cout << "3)" << test[j].questions[i].var_answers[2] << endl;
                        cout << "Correct answer - " << test[j].questions[i].answer << endl;
                    }
                    cout << "^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n\n";

                }
            }
            else
                cout << "Error";
            break; }

        case 6: {
            cout << "Which test results do you want to see?" << endl;
            cin >> choose;
            for (size_t i = 0; i < num_of_student; i++)
            {
                cout << "Name - " << test[choose].student[i].name << "\t" << test[choose].student[i].mark << endl;
            }
            break; }

        default:// вихід з програми
            throw;
        }
    }





}