B) Molar

Explanation:
Herbivores are animals that primarily eat plant material such as leaves, stems, and roots. Their teeth are adapted to efficiently process and grind down plant matter for digestion. Among the different types of teeth, herbivores have well-developed molars that are specifically designed for grinding and crushing plant material.

1. Function of molars in herbivores:
- Grinding: Herbivores need to break down tough plant fibers to extract nutrients. The molars have large, flat surfaces with ridges and valleys that help in grinding the food.
- Crushing: Some plants, like nuts or seeds, require extra force to break them open. Herbivores use their molars to exert pressure and crush these hard food items.
- Chewing: The molars work together with the jaw muscles to chew the food thoroughly, allowing for better digestion and nutrient absorption.

2. Structure of herbivorous molars:
- Broad and flat: The molars of herbivores are wider and flatter compared to carnivores or omnivores. This shape provides a larger surface area for grinding and masticating plant material.
- Ridges and cusps: The molars have ridges and cusps that help in breaking down tough plant fibers. These structures increase the efficiency of grinding and crushing.
- Enamel composition: The enamel covering the molars of herbivores is often thicker and more resistant to wear. This is because herbivorous diets can be abrasive due to the presence of fibrous plant material.

3. Examples of herbivores with well-developed molars:
- Cows: Cows have a large number of molars in their upper and lower jaws. These molars have a complex structure with multiple ridges, allowing them to efficiently break down tough plant material.
- Rabbits: Rabbits have continuously growing molars to compensate for the wear caused by constant grinding. Their molars are adapted for grinding fibrous grasses and other plant material.
- Elephants: Elephants have large, flat molars that are crucial for their plant-based diet. Their molars can weigh several kilograms and are used to grind down tough vegetation.

In summary, herbivores have well-developed molars that are specifically adapted for grinding, crushing, and chewing plant material. These molars have a broad, flat shape with ridges and cusps, allowing for efficient processing of fibrous plant matter.

B