Đọc bài đọc dưới đây và trả lời câu hỏi.

Flood stands amongst the most devastating natural catastrophes. Almost everyone is well aware of its negative impacts on human such as loss of human life, damage to property, destruction of crops, loss of livestocks, and deterioration of health conditions owing to waterborne diseases. However, flood can also have some positive impacts on the environment. In many natural systems, floods play the key role in maintaining the ecosystem functions and biodiversity. They link the river with the land surrounding it, recharge ground water systems and fill wetlands. Moreover, floodwater often carries both sediment and nutrients, so it helps enrich the land. For many species, flood trigger breeding events, migration, and dispesal. The environmental benefits of flooding can also help the economy through things such as increased fish production, recharge of groundwater resourses, and maintainance of recreational environments. While cycling of sediments and nutrients is essential to a healthy ecosystem, too much sediment and nutrient in a waterway lowers the downstream water quality. Other negative effects include loss of habitat, dispersal of weed species and the release of pollutants such as chemicals, heavy metals and debris. These can degrade aquatic habitats, lower water quality, reduce coastal production, and contaminate coastal food resources.

What does the passage mainly discuss?

A. Negative impacts of flood on human.

B. Negative impacts of flood on the ecosystem.

C. Effects of flood on the environment.