The correct answer is: B. Indirect
Indirect cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall. This is done by using a fan to circulate air over the windings, or by using a pump to circulate a liquid coolant through the windings.
Direct cooling is the process of dissipating the armature and field winding losses to the air surrounding the windings. This is done by using fins or other cooling devices to increase the surface area of the windings, and by using a fan to circulate air over the windings.
Conventional cooling is a term used to describe the traditional method of cooling electric motors. This method uses air to cool the motor’s windings.
Any of the above is not the correct answer because it is not a specific type of cooling.