Final answer:
The richest sources of phosphorus and calcium are found in dairy products such as milk, cheese, and yogurt, although other foods like vegetables and fish also contain these essential nutrients.
Step-by-step explanation:
The food group that yields the richest source of phosphorus and calcium is c) Dairy products. Phosphorus is present in many foods and is essential for bone strength, energy processing, and the formation of cell membranes. It's found in great quantities in dairy products, meats, cereals, beans, and nuts. Calcium also plays a crucial role in bone health and can be found abundantly in milk, cheese, and yogurt as well as in green leafy vegetables, broccoli, and fish with bones, like sardines and salmon. However, dairy products remain the most prominent source for people looking to increase their intake of calcium.