Screen utilization

So I am trying to create a simple quiz program. When I test play it within Unity it looks just fine, but when I install it on my phone, it is so small I can hardly see it. Please refer to the picture below. I have tried to use larger text in hopes it would fill in the unused area of the screen but of course that didn't work. How do I tell Unity to use the entire screen? Please see my script below. All I did was to create the scene was drag the Questionnaire2.cs script onto the Main Camera. Any help would be greatly appreciated. Thanks in advance.

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using UnityEngine; using System.Collections; using System.Collections.Generic;

public class Questionnaire2 : MonoBehaviour {

 public int questionTextSize;
 public int buttonTextSize;
 public int buttonWidth;
 public int buttonHeight;
 public int index;
 
 class Question
 {
     public string QuestionText;
     public List<string> Answers = new List<string>();
     public int CorrectAnswer;
 }

 List<Question> list = new List<Question>();

 Question GetQuestion()
 {
     int rand = Random.Range(0, list.Count);
     index = rand;
     return list[rand];  
 }

 void OnGUI()
 {
     //--------------------------For Debug Purposes--------------------------------
     //GUI.Label(new Rect(10, 10, 100, 20), "Questions: " + list.Count);
     //GUI.Label(new Rect(10, 30, 200, 20), "Current Question: " + index.ToString());
     //GUI.Label(new Rect(10, 60, 200, 20), "Current Answers: " + list[index].Answers);
     //-----------------------------------------------------------------------------

     //Custom setings...
     GUI.skin.label.fontSize = questionTextSize;
     GUI.skin.button.fontSize = buttonTextSize;
     GUI.skin.label.alignment = TextAnchor.UpperCenter;
     GUI.skin.label.alignment = TextAnchor.UpperCenter;

     //Display question...                                   
     GUI.Label(new Rect((Screen.width / 2) - (200 / 2), (Screen.height / 2) - (25 / 2) - 75, 200,200),list[index].QuestionText);
     
     //Display the answers.
     for (int i = 0; i <= 3; i++ )
     {
         if (GUI.Button(new Rect((Screen.width / 2) - (buttonWidth / 2), (Screen.height / 2) - (25 / 2) + i*30, buttonWidth,buttonHeight),list[index].Answers[i]))
         {
             //If correct answer...
             if (i == list[index].CorrectAnswer)
             {
                 Debug.Log("Correct");

                 if (index < list.Count)
                 {
                     list.Remove(list[index]);
                     GetQuestion();
                 }    //Here we would add the Ending...
                 else { Debug.LogError("Out Of Questions To Display"); }
             }
             else //if incorrect....
             {
                 Debug.Log("Incorrect");
                 GetQuestion();
             }
         }
     }

 }
 
 void Awake()
 {
     //Questions and answers are listed here. Index beginning at 0.
     //The CorrectAnswer property should set to the correct
     //Index of the correct answer in this first one you can see
     //Correct answer is index "3". 0, 1, 2, and 3("Four Text").
     list.Add(new Question());
     list[0].QuestionText = "What is 2 + 2?";
     list[0].Answers.Add("1");
     list[0].Answers.Add("2");
     list[0].Answers.Add("22");
     list[0].Answers.Add("4");
     list[0].CorrectAnswer = 3;
     
     list.Add(new Question());
     list[1].QuestionText = "What is 4 + 4?";
     list[1].Answers.Add("4");
     list[1].Answers.Add("44");
     list[1].Answers.Add("8");
     list[1].Answers.Add("100");
     list[1].CorrectAnswer = 2;
     
     list.Add(new Question());
     list[2].QuestionText = "What is 6 + 6?";
     list[2].Answers.Add("16");
     list[2].Answers.Add("9");
     list[2].Answers.Add("12");
     list[2].Answers.Add("6,000,000");
     list[2].CorrectAnswer = 2;
     
     list.Add(new Question());
     list[3].QuestionText = "What is 8 + 8?";
     list[3].Answers.Add("2");
     list[3].Answers.Add("88");
     list[3].Answers.Add("5");
     list[3].Answers.Add("16");
     list[3].CorrectAnswer = 3;

     //So to add a new question. Copy a block 
     //Like this one and paste it below. Then
     // Change the text in between ".."
     //And increment the number list[4] to list[5] 
     //and so on... The "3" on Correct answer 
     //is the index. 0,1,2,3  (or in human 1,2,3,4) 
     //So the 3 index is where it says 
     //list[4].Answers.Add("16");
     //the "4" is the question's index.
     list.Add(new Question());
     list[4].QuestionText = "What is 8 + 8?";
     list[4].Answers.Add("2");
     list[4].Answers.Add("88");
     list[4].Answers.Add("5");
     list[4].Answers.Add("16");
     list[4].CorrectAnswer = 3;

     //Get a question at runtime.
     GetQuestion();
 }

}

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