The correct answer is: a) Dams.
Siltation is the accumulation of sediment in a body of water, such as a river, lake, or reservoir. It can be caused by natural processes, such as erosion, or by human activities, such as deforestation or agriculture. Siltation can reduce the storage capacity of dams and reservoirs, and can also increase the risk of flooding.
Canals are artificial waterways that are used for irrigation, transportation, or drainage. They are typically lined with concrete or other materials to prevent erosion. Canals can also be affected by siltation, but the risk is generally lower than for dams and reservoirs.
Tanks are artificial reservoirs that are used for storing water. They are typically made of concrete or steel, and are often covered to prevent evaporation. Tanks are not as susceptible to siltation as dams and reservoirs, but they can still be affected if they are not properly maintained.
Hydropower projects use the power of moving water to generate electricity. They typically involve the construction of a dam or reservoir, which can cause siltation problems. Hydropower projects can also have other environmental impacts, such as the displacement of people and the loss of biodiversity.
In conclusion, the correct answer is: a) Dams. Dams are the most susceptible to siltation, which can reduce their storage capacity and increase the risk of flooding.