Beavers building a dam across a stream. Cattle walking and grazing in a grassland. Salmon making nests for their eggs in a stream. Tree seedlings growing and forming cracks in rocks.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Biotic forces can cause changes to the surface of Earth. Which is the best example of living organisms causing weathering?
Possibilities:
- Beavers building a dam across a stream.
- Cattle walking and grazing in a grassland.
- Salmon making nests for their eggs in a stream.
- Tree seedlings growing and forming cracks in rocks.

Tree seedlings growing and forming cracks in rocks.