Random instantiate?

Hello. I am trying to make a script where there are multiple possible object variants to spawn (in this case enemy types) and the it randomly spawns a set number of them at repeating intervals, but when I try my script I get the error " No appropriate version of 'UnityEngine.Random.Range' for the argument list '(UnityEngine.GameObject, UnityEngine.GameObject, UnityEngine.GameObject)' was found."

How can I fix my script? Thanks :)

var A : GameObject;
var B : GameObject;
var C : GameObject;

if (Projectile.Defeat < 200 && Projectile.Defeat > 80)
    {   yield WaitForSeconds(5.0); 
        Instantiate(Random.Range(A,B,C), position, Quaternion.identity);
    }

EDIT For being organized, is there a better way to instantiate multiple objects other than copying the instantiate part of the script like this?

   Instantiate(objs[(Random.Range(0, 3))], new Vector3(Random.Range(481.5735, 559.3441), -791.811, Random.Range(380.1254, 420.0663)), Quaternion.identity);
    Instantiate(objs[(Random.Range(0, 3))], new Vector3(Random.Range(481.5735, 559.3441), -791.811, Random.Range(380.1254, 420.0663)), Quaternion.identity);
   Instantiate(objs[(Random.Range(0, 3))], new Vector3(Random.Range(481.5735, 559.3441), -791.811, Random.Range(380.1254, 420.0663)), Quaternion.identity);

You could make an array of GameObjects instead, get a random number between 0-3, and use it as the index, I think.

var objs : GameObject[];

// Populate array with objects A, B, and C here

if (Projectile.Defeat < 200 && Projectile.Defeat > 80) {
    yield WaitForSeconds(5.0);
    Instantiate(objs[(Random.Range(0, objs.Length))], position, Quaternion.identity);
}

To do a random position as well, you could replace 'position' above with a random Vector3, within a range you decide (xMin & Max, etc):

new Vector3(Random.Range(xMin, xMax), Random.Range(yMin, yMax), Random.Range(zMin, zMax))

And to create more than one object (3 objects, for example) :

...
yield WaitForSeconds(5.0);
for (var i = 0; i < 3; i++) {
    Instantiate(objs[(Random.Range(0, objs.Length))], position, Quaternion.identity);
}