Students observe two hills, Hill A and Hill B. After a heavy rainstorm, the students observe that Hill A has more loose soil at the bottom than Hill B. Which sentence best describes what most likely caused the loose soil?

1. Hill A has fewer plants than Hill B
2. Hill A erodes more slowly than Hill B
3. Hill A has a slope not as steep as Hill B
4. Hill A receives less average rainfall than Hill B

If Hill A has more loose soil as compared to hill B, then less vegetation on Hill A can be one of the reasons behind it. The roots of vegetation like herbs, shrubs, trees etc. bind and hold the soil tightly and hence restrict soil erosion because in such circumstances the top soil will not be blown away easily by wind or water flow. But, a barren land which doesn't have much vegetation fails to do so. In such region, the top soil will be loose so it will get depleted easily in case of flood or water flow due to heavy rainstorm.