Random.Range is picking two gameobjects instead of one

I have created code for a question generator but every now and then my random.range is picking two of my gameobjects(out of 20). The code should work but something is causing it to pick two. Is it a bug with unity or the code itself?

  public void Start()
{
    box_QA.SetActive(false);

    calculate = 0;

         for (int n = 1; n < 21; n++)
    {
        list.Add(n);

    }



}

void Update()
{
        DeleteQuestions();


}

public void CheckQuestion() {

    index = Random.Range(0, list.Count - 1);
    i = list[index];
    Debug.Log(i);
    list.RemoveAt(index);

}

public void WhatQuestion()
{


    CheckQuestion();

    if (i == 1)
    {

        Question1.SetActive(true);

        Question2.SetActive(false);
        Question3.SetActive(false);
        Question4.SetActive(false);
        Question5.SetActive(false);
        Question6.SetActive(false);
        Question7.SetActive(false);
        Question8.SetActive(false);
        Question9.SetActive(false);
        Question10.SetActive(false);
        Question11.SetActive(false);
        Question12.SetActive(false);
        Question13.SetActive(false);
        Question14.SetActive(false);
        Question15.SetActive(false);
        Question16.SetActive(false);
        Question17.SetActive(false);
        Question18.SetActive(false);
        Question19.SetActive(false);
        Question20.SetActive(false);



    }