It is a light coloured band that is present the earthworm instead of the 14th, 15th and 16th segment in the body of an earthworm. Clitellum plays an important role in the process of copulation by secretion of mucus and cocoon for eggs. So, the correct answer is option c

The clitellum, also known as the cingulum, is a specialized glandular structure found in earthworms. It plays a crucial role in reproduction and is responsible for the formation of a cocoon in which the eggs are fertilized and develop into new offspring. The clitellum is located in a specific segment(s) of the earthworm's body.

The correct answer to the question is option 'C', which states that the clitellum is present in segments 14, 15, and 16. Let's discuss this in detail:

1. Anatomy of an Earthworm:
- An earthworm is divided into several segments called metameres.
- Each segment has its own set of structures, such as muscles, nerves, and reproductive organs.
- The segments are numbered sequentially from anterior (head end) to posterior (tail end).

2. Location of the Clitellum:
- The clitellum is not present in all segments of an earthworm's body.
- It is located in a specific region, typically closer to the anterior end.
- In most earthworm species, the clitellum spans segments 14, 15, and 16.

3. Formation of the Cocoon:
- The clitellum is responsible for producing a thick, gelatinous secretion.
- This secretion contains eggs from the female reproductive organs and sperm from the male reproductive organs.
- As the earthworm moves forward, the clitellum slides over the anterior end of the body, picking up the eggs and sperm.
- The secretion hardens to form a protective cocoon around the eggs and sperm.

4. Development of Offspring:
- Fertilization occurs within the cocoon, and the eggs develop into young earthworms.
- The development process takes place inside the cocoon, and the young earthworms hatch out as fully formed individuals.
- The cocoon is eventually deposited in the soil, where the young earthworms emerge and continue their life cycle.

In conclusion, the clitellum in earthworms is present in segments 14, 15, and 16. This specialized structure plays a vital role in reproduction by producing a cocoon in which the eggs and sperm are enclosed for fertilization and development of the offspring.