The correct answer is option 3: Iron. Iron is an essential mineral that is needed for various bodily functions, including the production of red blood cells and oxygen transportation. Leafy vegetables, such as spinach, kale, and broccoli, are known to be rich sources of iron. Iron deficiency can lead to anemia and fatigue, so it is important to consume foods that are high in iron. Phosphorous, zinc, and calcium are also important nutrients, but they are not typically found in high amounts in leafy vegetables. Phosphorous is important for bone health and energy production, zinc plays a role in immune function and wound healing, and calcium is necessary for strong bones and teeth.