The correct answer is D. all above factors.
Corrosion is the deterioration of a material due to chemical reaction with its environment. In the case of underground metal work, the environment is the soil. The extent of corrosion depends on a number of factors, including the amount of moisture in the soil, the type of metal, and the type of soil chemicals.
Moisture is necessary for corrosion to occur. Without moisture, there is no way for the metal to react with the chemicals in the soil. The amount of moisture in the soil can vary depending on the climate and the type of soil.
The type of metal also affects the rate of corrosion. Some metals, such as iron, are more susceptible to corrosion than others. The type of metal used for underground metal work should be chosen carefully to minimize the risk of corrosion.
The type of soil chemicals can also affect the rate of corrosion. Some chemicals, such as acids, can accelerate corrosion. The type of soil should be considered when choosing a metal for underground metal work.
In conclusion, the extent of corrosion in underground metal work depends on a number of factors, including the amount of moisture in the soil, the type of metal, and the type of soil chemicals. All of these factors should be considered when choosing a metal for underground metal work.