Step 1: Understanding the Concept:
Calcium is an essential mineral required for building and maintaining strong bones and teeth, as well as for various other bodily functions. The question asks to identify sources of calcium from the given food items.
Step 2: Detailed Explanation:
- Milk: Milk is widely recognized as one of the best dietary sources of calcium.
- Curd (Yogurt): Curd is a dairy product made by fermenting milk. It is also an excellent source of calcium, often containing amounts comparable to or even higher than milk.
- Paneer (Cottage Cheese): Paneer is a type of fresh cheese made from milk. As a concentrated milk product, it is also a rich source of calcium.
Since all three are dairy products, they are all significant sources of calcium.
Step 3: Final Answer:
Milk, Curd, and Paneer are all good sources of calcium. Therefore, the correct option is All of these.