Final answer:
Building a dam upstream can have both positive and negative impacts on the people downstream. It can improve water quality but reduce water availability for drinking and irrigation.
Step-by-step explanation:
Building a dam upstream can have both positive and negative impacts on the people who live downstream.
On one hand, the people downstream may experience an improvement in the quality of their water supply. This is because the dam helps in trapping sediment and pollutants, leading to cleaner water that is more suitable for drinking.
On the other hand, the people downstream may face challenges related to water availability. The construction of a dam can reduce the water flow downstream, resulting in less water for drinking and irrigation of crops. Therefore, option B is the correct answer as the people downstream would have less water for drinking and irrigation of crops due to the dam construction upstream.
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