Play sound by pressing button

I need help. This is script:
using UnityEngine;
using System.Collections;

public class FS : MonoBehaviour {

public AudioClip MyAudio;

// Use this for initialization
void Start () {
	if(Input.GetKeyDown(KeyCode.W)) {
		audio.PlayOneShot(MyAudio);
}
}

}
Whats wrong??

You put the code on Start so the game will only check at begining of the scene.
Try putting the code in Update.

don’t put this code on " void Start () " !

try putting in Update