The fertility of the soil is an important factor in the selection of site for a ...

The question is asking why the fertility of the soil is important when selecting a site for a fish pond.

When it comes to fish ponds, having a fertile soil is crucial. Fertile soil contains nutrients that are necessary for the growth of plants. In the context of a fish pond, these plants are usually lower plants like algae or aquatic plants. These plants serve as a source of food for the fish.

Option B is the correct answer because a fertile soil will stimulate the growth of these lower plants, providing a natural and abundant food source for the fish. This is important for the overall health and growth of the fish population in the pond.

The other options are not directly related to the fertility of the soil. Option A suggests that a fertile soil will encourage the growth of trees within the pond, which is not desirable as it can shade the pond and hinder the growth of aquatic plants. Option C states that a fertile soil will add minerals to the water for the fish's resistance to diseases, which is not accurate as the soil does not directly add minerals to the water. Option D claims that a fertile soil will prevent the pond from drying up, which is not necessarily true as the fertility of the soil does not directly affect the water retention of the pond. Lastly, Option E suggests that a fertile soil will lower the temperature of the pond water for the survival of fish, which is not a direct effect of soil fertility.

In summary, when selecting a site for a fish pond, it is important to consider the fertility of the soil because a fertile soil will stimulate the growth of lower plants that serve as a food source for the fish.