Know whether prefab or instance

How can I determine whether a reference points to a prefab or instance?

Here's my custom script:

 public class MyClas : MonoBehavior
 {
   public GameObject[] objects = new GameObject[0];
 
   void Start() {
     for (int i=0; i < objects.Length; +=i) {
       Instantiate(objects[i], ...)
       // Destroy the original if it wasn't a prefab
       if (???????) {
         Destroy(objects[i])
       }
     }

What goes in the ??????

Thanks!