Unity doesn't recognize "List" object type (Linq)

Going off of another user’s suggestion, I have tried to use a Linq type object called “List”. I apologize if I am not using the correct terminology. I am still wrapping my head around Linq.

The error message: “The name ‘List’ does not denote a valid type (‘not found’). Did you mean UnityEngine.Light?”

The affected code:

import System.Linq;


private var availablePositions : List.<Transform>;
//Allows assignation through the Inspector of the two possible positions from which the Spawn function will
//later randomly select.
var blackElves : GameObject[];
//Populates array with enemy elves
var fatElfCompanion : GameObject;
var shortElfCompanion : GameObject;
var strongElfCompanion : GameObject;
var smartElfCompanion : GameObject;
var fastElfCompanion : GameObject;
var toughElfCompanion : GameObject;
var uglyElfCompanion : GameObject;
var youngElfCompanion : GameObject;
//links each enemy elf with a partner


function Start () 
{
 availablePositions = attackPositions.ToList();
}
//lists available attack positions of enemy elf and his partner.

function Update () {

}	

function OnTriggerEnter(col : Collider)
{
	if(col.gameObject.tag == "Player")
	{
		yield new WaitForSeconds(3.0);
		Spawn;
	}
}
//When player enters this zone, the function "Spawn" is called after three seconds.

function Spawn ()
{
	
	var position = availablePositions[Random.Range(0, availablePositions.Length)];
	availablePositions.Remove(position);
	//One position is selected at random from two possibilities. The position selected is removed from set of possibilities.
	var attackElf = Instantiate(blackElves[(Random.Range(0, blackElves.Length))], position.position, Quaternion.identity);
	//One of the enemy elves is selected from the array and named "attack Elf". It is assigned to the randomly selected position.
	if(attackElf.tag == "fatElf")
	{
		var companionElf = Instantiate(fatElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "shortElf")
	{
		companionElf = Instantiate(shortElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "strongElf")
	{
		companionElf = Instantiate(strongElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "smartElf")
	{
		companionElf = Instantiate(smartElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "fastElf")
	{
		companionElf = Instantiate(fastElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "toughElf")
	{
		companionElf = Instantiate(toughElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "uglyElf")
	{
		companionElf = Instantiate(uglyElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else if(attackElf.tag == "youngElf")
	{
		companionElf = Instantiate(youngElfCompanion, availablePositions[0].position, Quaternion.identity);
	}else
	{
		Debug.Log("Error");
	}
}



//A second, "Companion Elf" is instantiated at the other remaining position. It is not selected at random. It
//must be the concomitant of the "Attack Elf" previously selected.

Ugh sorry - perhaps you need to import System.Collections.Generic too…

#pragma strict

import System.Linq;
import System.Collections.Generic;

private var availablePositions : List.<Transform>;
var blackElves : GameObject[];
//Populates array with enemy elves
var fatElfCompanion : GameObject;
var shortElfCompanion : GameObject;
var strongElfCompanion : GameObject;
var smartElfCompanion : GameObject;
var fastElfCompanion : GameObject;
var toughElfCompanion : GameObject;
var uglyElfCompanion : GameObject;
var youngElfCompanion : GameObject;
var attackPositions : Transform[];
//links each enemy elf with a partner


function Start () 
{
 availablePositions = attackPositions.ToList();
}
//lists available attack positions of enemy elf and his partner.

function Update () {

}   

function OnTriggerEnter(col : Collider)
{
    if(col.gameObject.tag == "Player")
    {
       yield new WaitForSeconds(3.0);
       Spawn();
    }
    }
//When player enters this zone, the function "Spawn" is called after three seconds.

function Spawn ()
{
    var position = availablePositions[Random.Range(0, availablePositions.Count)];
    availablePositions.Remove(position);
    //One position is selected at random from two possibilities. The position selected is removed from set of possibilities.
    var attackElf = Instantiate(blackElves[(Random.Range(0, blackElves.Length))], position.position, Quaternion.identity);
    //One of the enemy elves is selected from the array and named "attack Elf". It is assigned to the randomly selected position.
    if(attackElf.tag == "fatElf")
    {
       var companionElf = Instantiate(fatElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "shortElf")
    {
       companionElf = Instantiate(shortElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "strongElf")
    {
       companionElf = Instantiate(strongElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "smartElf")
    {
       companionElf = Instantiate(smartElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "fastElf")
    {
       companionElf = Instantiate(fastElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "toughElf")
    {
       companionElf = Instantiate(toughElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "uglyElf")
    {
       companionElf = Instantiate(uglyElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else if(attackElf.tag == "youngElf")
    {
       companionElf = Instantiate(youngElfCompanion, availablePositions[0].position, Quaternion.identity);
    }else
    {
       Debug.Log("Error");
    }
}