The correct answer is Option 4: Stigma.

Saffron spice is derived from the saffron crocus plant, scientifically known as Crocus sativus. The saffron crocus is a flowering plant that belongs to the iris family. The spice is obtained from the stigma, which is a part of the female reproductive organ of the flower.

Here`s a detailed explanation:

1. Loaf: The term "loaf" typically refers to a shaped mass of bread or a similar food item. It is not related to saffron production or the saffron crocus plant.

2. Petal: While petals are part of the flower structure, they are not used to produce saffron spice. Saffron is derived from the reproductive parts of the flower, not the petals.

3. Sepal: Sepals are small, leaf-like structures located at the base of the flower. They protect the developing bud but are not involved in saffron production.

4. Stigma: The stigma is a thread-like structure that is part of the female reproductive system of the flower. It is responsible for receiving pollen during fertilization. In the case of saffron, the stigma is the part that is harvested and dried to produce the saffron spice. The bright red-orange strands that are commonly associated with saffron are actually the dried stigmas of the saffron crocus flowers.

Saffron is a highly prized spice known for its distinct flavor, aroma, and vibrant color. It is used in various culinary preparations, including rice dishes, desserts, and beverages. It is also used in traditional medicine and has been studied for its potential health benefits.

It is important to note that saffron production is labor-intensive, as each saffron crocus flower only produces three stigmas, which must be handpicked. It takes a large number of flowers and careful processing to obtain a relatively small quantity of saffron spice, which contributes to its high cost in the market.

Overall, the stigma of the saffron crocus plant is used to make saffron spice, making Option 4 the correct answer.