The correct answer is: B. windings
The windings of a transformer are the parts that carry the current, and therefore they are the parts that generate the most heat. The core of the transformer is made of a material that has a high magnetic permeability, which means that it can easily be magnetized. This magnetization causes the core to heat up, but the heat generated by the core is much less than the heat generated by the windings.
The tank of the transformer is the outer shell that protects the windings and core. The tank is made of a material that has a low thermal conductivity, which means that it does not transfer heat very well. This helps to keep the heat generated by the windings and core from escaping, which helps to keep the transformer cool.
In conclusion, the maximum temperature rise will occur in the windings of a transformer. This is because the windings are the parts that carry the current, and therefore they are the parts that generate the most heat.