Answer:
Option B and C
Explanation:
Construction of hydro-power dam is generally done to produce electricity from water, provide efficient irrigation and navigation services. Therefore, there is no chance of decrease in economic activity. In fact, economic activities increases further after dam construction.
However, in order to capture the land for dam construction several local people are displaced from their native locations. This is one of the negative effect of construction of hydro-power dam.
Also, in order to produce electricity water is stored at greater heights by withdrawing water from canal or river. This causes reduction in water level.
Hence, option B and C are correct
