The pH of a fertile soil is usually around

Answer: Option C

The pH of fertile soil is usually around 6 - 7.
Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Soils which contain high levels of particular clays with high swelling properties, such as smectites, are often very fertile.
The correct balance is where the soil pH is between 5.5 and 7.5. Plants can excrete H⁺ into the soil through the synthesis of organic acids and by that means, change the pH of the soil near the root and push cations off the colloids, thus making those available to the plant.