Step 1: Understanding the Concept:
The question asks to identify a key nutrient found in green leafy vegetables.
Step 2: Detailed Explanation:
Green leafy vegetables like spinach, kale, and broccoli are known to be nutritional powerhouses. While they contain small amounts of protein and carbohydrates (sugars like glucose), they are most celebrated for being exceptionally rich in vitamins (like Vitamin A, C, K) and mineral salts. These include essential minerals such as iron, calcium, potassium, and magnesium. Among the given options, "Mineral salts" is the most accurate and significant nutritional component for which green leafy vegetables are recommended.
Step 3: Final Answer:
Green leafy vegetables are a primary source of vitamins and mineral salts.