The correct answer is: C. 100 kV
Dielectric strength is the maximum electric field strength that an insulating material can withstand without breaking down and allowing current to flow. The dielectric strength of transformer oil is typically around 100 kV per millimeter. This means that if a transformer oil is placed between two electrodes with a spacing of 1 millimeter, the maximum voltage that can be applied without breaking down the oil is 100 kV.
The dielectric strength of transformer oil is important because it helps to prevent arcing and other electrical failures in transformers. Arcing can cause damage to the transformer and can even lead to fires. By maintaining a high dielectric strength, transformer oil helps to protect the transformer and ensure its safe operation.
The dielectric strength of transformer oil can be affected by a number of factors, including the temperature of the oil, the presence of contaminants, and the type of insulation used in the transformer. It is important to regularly test the dielectric strength of transformer oil to ensure that it is within the required specifications.
The other options are incorrect because they are not within the typical range of dielectric strengths for transformer oil.