The correct answer is option 'C' - Fleece of sheep.

Wool is a natural fiber that is obtained from the fleece or hair of sheep. It is one of the most commonly used animal fibers due to its excellent properties such as warmth, softness, and durability. Let's understand in detail how woolen fibers are obtained from the fleece of sheep.

Process of Obtaining Wool:
1. Shearing: The process of removing the fleece or hair from the sheep's body is known as shearing. It is done once a year during spring or early summer when the sheep's wool is long and thick. Shearing is usually carried out by skilled professionals called shearers who use electric clippers to remove the wool. It is important to shear the sheep carefully without hurting them.

2. Fleece: The fleece is the entire coat of wool that is removed from the sheep's body during shearing. It consists of both the long coarse outer hair known as guard hair and the soft, fine inner layer called the undercoat or true wool. The undercoat is the most valuable part of the fleece used for making woolen fibers.

3. Sorting and Grading: Once the fleece is removed, it is sorted and graded based on its quality. This process involves separating the different types of wool fibers based on their length, fineness, color, and cleanliness. The highest quality wool is usually obtained from the shoulders and sides of the sheep, while the lower quality wool comes from the belly and legs.

4. Scouring: After sorting, the fleece is thoroughly washed to remove dirt, grease, and other impurities. This process is known as scouring and is done using warm water and mild detergent. The washed fleece is then rinsed and dried to obtain clean wool fibers.

5. Carding: The next step in the process is carding, where the fibers are aligned in the same direction to remove any tangles or knots. Carding is done by passing the wool through a series of carding combs or rollers, which separate and straighten the fibers. This process helps in obtaining a smooth and even texture.

6. Spinning: Once the wool fibers are carded, they are ready to be spun into yarn. Spinning is the process of twisting the fibers together to form a continuous thread. This can be done using a spinning wheel or a spinning machine. The resulting yarn can be further processed to create different types of woolen fabrics.

In conclusion, woollen fibers are obtained from the fleece of sheep through a series of processes including shearing, sorting and grading, scouring, carding, and spinning. The quality of wool depends on factors such as the breed of sheep, climate, and the care taken during processing. Wool is a versatile and sustainable material that finds numerous applications in the textile industry.