Undefined symbols for architecture x86_64:
      "Question::display()", referenced from:
      _main in QuizDriver-e52a2c.o
      "Question::getKey() const", referenced from:
      _main in QuizDriver-e52a2c.o
    ld: symbol(s) not found for architecture x86_64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)

#include <iostream>
#include <iomanip>
using namespace std;

#include "Question.h"

int main()
{
    Question q1;
    Question q2;
    Question q3;
    Question q4;
    string q1Stem = "1. What name is given to half of a Byte (4 bits)?";
    string q1Answers [] = {"Nibble","Ort","Scrap","Snippet"}; //answer A
    string q2Stem = "2. Which country is home to the Kangaroo?";
    string q2Answers [] = {"China","India","Mexico","Australia"}; //answer D
    string q3Stem = "3. What do you use to measure an angle?";
    string q3Answers [] = {"Compass","Protractor","Ruler","T-Square"}; //ans B
    string q4Stem =
    "4. The Great Sphinx has the head of a human and the body of a what?";
    string q4Answers [] = {"Camel","Eagle","Lion","Alligator"}; //answer C
    string q5Stem =
    "5. What is the flat rubber disc used in a game of ice hockey?";
    string q5Answers [] = {"Birdie","Puck","Dart","Tile"}; //answer B

    q1.display();
    cout << endl;
    q2.display();
    cout << endl;
    q3.display();
    cout << endl;
    q4.display();
    cout << endl;

    cout << "Answers:" << endl;
    cout << q1.getKey() << " " << q2.getKey() << " " << q3.getKey() <<
    " " << q4.getKey() << endl;

    return 0;
}

#include <string>
using namespace std;

class Question
{
public:
    string stem;
    string answers[4];
    char key;
    void setStem(string);
    string getStem() const;
    void setAnswers(string []);
    string getAnswer(int);
    void setKey(char);
    char getKey() const;

    void display();
};