CodeIQ presents, Unity Editor Seminar. Question1. I checked How to use MenuItem's 2nd argument.

Question1Editor.cs

using UnityEngine;
using UnityEditor;
using System.Collections;

public class Question1Editor : Editor {
  [MenuItem("Editor10/Question1")]
	static void Question1_Basic(){}

	[MenuItem("Editor10/Question1_ #&n",false)]
	static bool Validateaaa()
	{
		Debug.Log("Validate");
		return Selection.activeTransform;
		// http://docs.unity3d.com/Documentation/ScriptReference/Selection-activeTransform.html
	}
	[MenuItem("Editor10/Question1_ #&n",true)]
	static void Question1_Practical()
	{
		Debug.Log("1");
		GameObject childObj = new GameObject();
		if(childObj == null) return;
		childObj.transform.parent = Selection.activeGameObject.transform;
	}

	[MenuItem("Editor10/Question1_ #&n")]
	static void Question1_Practical2()
	{
		Debug.Log("2");
		GameObject childObj = new GameObject();
		if(childObj == null) return;
		childObj.transform.parent = Selection.activeGameObject.transform;
	}

}