Which of the following best describes nested concepts? a. A planning technique to achieve unity of purpose whereby each succeeding echelon's concept of operations is aligned by purpose with the higher echelons' concept of operations. b. A statement that directs the manner in which subordinate units cooperate to accomplish the mission and establishes the sequence of actions the force will use to achieve the end state. c. A short sentence or paragraph that describes the organization's essential task(s) and purpose (action to be taken and reason for doing so). d. The desired or intended result of the tactical operation stated in terms relating to the enemy or to the desired situation