Explanation:

- Sheet erosion: This is the initial stage of soil erosion where a thin layer of soil is removed by runoff water. It's more uniform and lacks prominent features.

- Splash erosion: Occurs when raindrops hit the soil surface, causing soil particles to be displaced. It primarily affects the top layer.

- Rill erosion: ? This is the next stage after sheet erosion. Finger-like channels begin to form as water runoff becomes more concentrated. With time, these can develop into deeper channels, known as gullies.

- Gully erosion: Results when rills deepen and widen significantly, creating larger, more pronounced channels that are challenging to repair.

- None of the above: This option is incorrect as rill erosion follows sheet erosion.

Rill erosion is the correct answer.