The correct answer is option 'C' - the typhlosole in an earthworm increases the absorptive area of the intestinal epithelium.

The typhlosole is a longitudinal fold in the intestinal wall of earthworms. It runs along the mid-dorsal line of the intestine and increases the surface area available for absorption of nutrients.

To understand why the typhlosole increases the absorptive area, let's take a closer look at the structure and function of the earthworm's digestive system.

1. Structure of the Digestive System:
- The digestive system of an earthworm consists of a mouth, pharynx, esophagus, crop, gizzard, intestine, and anus.
- The intestine is the main site of digestion and absorption.
- The intestine is a long tube lined with a specialized epithelial layer that is responsible for the absorption of nutrients.

2. Function of the Typhlosole:
- The typhlosole is a fold of the intestinal wall that protrudes into the lumen of the intestine.
- Its main function is to increase the surface area of the intestinal epithelium.
- By increasing the surface area, the typhlosole provides more space for the absorption of nutrients from the ingested food.
- This increased surface area allows for more efficient absorption and digestion of food.

3. Nutrient Absorption:
- Earthworms are detritivores, which means they feed on decaying organic matter in soil.
- The ingested organic matter passes through the earthworm's digestive system, where it is broken down into simpler molecules.
- These simpler molecules, such as sugars, amino acids, and fatty acids, are then absorbed across the intestinal epithelium and into the bloodstream.
- The absorbed nutrients are then transported to different parts of the earthworm's body for energy production and growth.

In conclusion, the typhlosole in an earthworm increases the absorptive area of the intestinal epithelium, allowing for more efficient absorption of nutrients from the ingested food. This adaptation helps earthworms extract as much nutrition as possible from the organic matter they consume, supporting their survival and growth.