"Can't add script behaviour AICharacterControl. The script needs to derive from MonoBehaviour!" ?

I'm trying to make a typewriter-like text using another question on here but I keep on getting this pop-up saying I'm not able to do so. How do I fix it?

Here's my script:

 string[] vicinityText = new string[2]
     {
         "I see you're unfamiliar with this place... here's some basic enemies. Fight or die trying.",
         "Easy enough, right? Now let's test your mathematical knowledge."
     };
 
     public Text vicinityTalkBox;
     int currentTextDisplayed = 0;
 
     private void Awake()
     {
         StartCoroutine(AnimateText());
     }
 
     IEnumerator AnimateText()
     {
         for (int x = 0; x < vicinityText[currentTextDisplayed].Length + 1; x++)
         {
             vicinityTalkBox.text = vicinityText[currentTextDisplayed].Substring(0, x);
             yield return new WaitForSeconds(0.3f);
         }
     }

,I'm trying to add a script that adds coroutines (I'm unexperienced with them) but this pop-up saying that I can't add AICharacterControl repeatedly appears. How do I fix it? Here's my script:

 string[] vicinityText = new string[2]
     {
         "I see you're unfamiliar with this place... here's some basic enemies. Fight or die trying.",
         "Easy enough, right? Now let's test your mathematical knowledge."
     };
 
     public Text vicinityTalkBox;
     int currentTextDisplayed = 0;
 
     private void Awake()
     {
         StartCoroutine(AnimateText());
     }
 
     IEnumerator AnimateText()
     {
         for (int x = 0; x < vicinityText[currentTextDisplayed].Length + 1; x++)
         {
             vicinityTalkBox.text = vicinityText[currentTextDisplayed].Substring(0, x);
             yield return new WaitForSeconds(0.3f);
         }
     }