Horses are commonly used for transportation in hilly areas and deserts for several reasons.

1. Physical Adaptations:
- Horses have strong legs and hooves that allow them to navigate through rough terrain, including steep slopes and rocky surfaces. Their muscular build enables them to carry heavy loads without easily tiring.
- The shape of their bodies, with a long neck and powerful hindquarters, provides stability and balance while climbing uphill or descending steep slopes.
- Horses are also able to withstand extreme temperatures and harsh weather conditions, making them well-suited for desert environments.

2. Surefootedness:
- Horses have a natural sense of balance and are known to be surefooted. This means they have the ability to carefully place their feet on uneven surfaces, preventing slips and falls on treacherous terrain.
- Their agility and nimbleness help them maneuver through narrow and winding pathways, making them ideal for traversing hilly areas and desert landscapes.

3. Endurance:
- Horses have a remarkable capacity for endurance, allowing them to travel for long distances without tiring quickly. This makes them suitable for covering extensive terrains in hilly areas and deserts, where other modes of transportation may struggle.

4. Versatility:
- Horses can be used not only for transportation but also for various other tasks in hilly areas and deserts. They can assist with agriculture, carry goods, and even provide recreational activities such as horseback riding and racing.
- Their ability to form a bond with humans and their trainable nature make them valuable companions in these regions.

Overall, horses possess a unique combination of physical adaptations, surefootedness, endurance, and versatility that make them the preferred choice for transportation in hilly areas and deserts. Their qualities enable them to navigate challenging terrains, withstand harsh conditions, and cover long distances efficiently and safely.