Corona loss is a phenomenon that occurs in high voltage transmission lines when the electric field strength at the surface of the conductor exceeds a certain critical value. This causes the air surrounding the conductor to ionize and conduct electricity, resulting in a loss of power. The corona loss increases with a decrease in conductor size and an increase in supply frequency. Let's understand why this is the case in detail.

1. Corona Loss and Conductor Size:
- Corona loss is directly related to the electric field strength at the surface of the conductor. A smaller conductor size means a higher electric field intensity at the surface.
- As the conductor size decreases, the electric field gradient increases, leading to a higher chance of ionization of the surrounding air.
- Consequently, there is an increase in the corona loss as the conductor size decreases.

2. Corona Loss and Supply Frequency:
- The corona loss is also influenced by the supply frequency. Higher frequencies result in higher corona losses.
- At higher frequencies, the time available for the charged particles to recombine and neutralize decreases.
- As a result, more ionization occurs, leading to an increase in corona loss.

Explanation of the Correct Answer (Option A):
- Option A states that the corona loss increases with a decrease in conductor size and an increase in supply frequency.
- This answer is correct because a decrease in conductor size leads to a higher electric field intensity at the surface, resulting in increased corona loss.
- Additionally, an increase in supply frequency reduces the time available for charged particles to recombine, leading to a higher corona loss.

In summary, corona loss increases with a decrease in conductor size and an increase in supply frequency. This is because a smaller conductor size leads to a higher electric field intensity at the surface, while an increase in supply frequency reduces the time available for charged particles to recombine. It is important to consider these factors in the design and operation of high voltage transmission lines to minimize corona losses and improve overall system efficiency.