If slope is steep and soil is eroded, why will plant growth be difficult?

Correct answer: Because erosion reduces root support and nutrients

The direct answer is B: erosion reduces root support and nutrients. Plant growth needs suitable soil, water, nutrients, and a stable place for roots. A steep slope allows rainwater to flow quickly downhill. This fast flow can carry away the upper fertile soil, a process called soil erosion. Step by step: the steep slope increases runoff; runoff removes soil particles and humus; the soil becomes thinner and poorer; roots get less support, water, and nutrients; plant growth becomes difficult. Option B correctly describes both major effects. Option A is wrong because a slope does not always provide more nutrients; steep slopes commonly lose nutrients through runoff. Option C is wrong because erosion does not increase rainfall. Rainfall is an atmospheric process, while erosion is the removal and transport of soil. Option D is wrong because sunlight can reach steep slopes; the problem is unstable, nutrient-poor soil, not the complete absence of sunlight. The exam cue is “steep slope plus erosion equals thin soil and weak roots.”