A. IF B. UNLESS C. WHEN D. IN CASEREAD THE FOLLOWING PASSAGE AND A...

23. A. If

B. Unless

C. When

D. In case

Read the following passage and answer the question

Flood stands amongest 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 live stocks, 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 resources, and

maintenance 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.