The slowest mode of land transport among the given options is a bicycle.

Explanation:

Comparing the Speeds of Different Modes of Transport:

- Scooter: Scooters are motorized vehicles that can reach relatively high speeds compared to other modes of transport. They are faster than bicycles and can travel at speeds of around 30-40 miles per hour (48-64 kilometers per hour) depending on the model.
- Car: Cars are also motorized vehicles that can travel at varying speeds depending on the type of car and road conditions. On average, cars can reach speeds of 60-70 miles per hour (96-112 kilometers per hour) on highways, making them faster than both scooters and bicycles.
- Bus: Buses are larger vehicles designed to transport a larger number of passengers. They have relatively lower maximum speeds compared to scooters and cars. On average, buses travel at speeds of around 30-40 miles per hour (48-64 kilometers per hour), similar to scooters.
- Bicycle: Bicycles are non-motorized vehicles that rely on human power to move. They are the slowest mode of land transport among the given options. The maximum speed a bicycle can achieve depends on various factors such as the cyclist's strength, terrain, and road conditions. On average, a cyclist can travel at speeds of around 12-15 miles per hour (19-24 kilometers per hour), which is significantly slower than the other options.

Factors Affecting Bicycle Speed:

- Cyclist's Strength: The speed at which a cyclist can pedal depends on their physical fitness and strength. If a cyclist is not very fit or lacks strength, they may not be able to pedal as fast, resulting in slower speeds.
- Terrain: The type of terrain also plays a crucial role in determining a bicycle's speed. Uphill slopes require more effort and slow down the cyclist, while downhill slopes allow for faster speeds. Flat terrains are generally easier to cycle on and can result in relatively higher speeds.
- Road Conditions: The condition of the road surface can affect a bicycle's speed. Smooth, well-paved roads allow for smoother pedaling and faster speeds, while rough or uneven surfaces can slow down the cyclist.

Conclusion:

In conclusion, the slowest mode of land transport among the given options is a bicycle. Bicycles rely on human power, have lower maximum speeds compared to motorized vehicles, and can be affected by factors such as the cyclist's strength, terrain, and road conditions.