The correct answer is: C. Long shunt compound generator
A series generator is a type of DC generator in which the field winding is connected in series with the armature winding. This means that the current flowing through the field winding is the same as the current flowing through the armature winding. This type of generator is not typically used for charging automobile batteries because it produces a very high output voltage when the load is low.
A shunt generator is a type of DC generator in which the field winding is connected in parallel with the armature winding. This means that the current flowing through the field winding is independent of the current flowing through the armature winding. This type of generator is more commonly used for charging automobile batteries because it produces a more constant output voltage over a wider range of loads.
A long shunt compound generator is a type of DC generator in which the field winding is connected in series with the armature winding and also in parallel with a resistor. This type of generator combines the features of both series and shunt generators. It produces a higher output voltage than a shunt generator when the load is low, and it produces a more constant output voltage over a wider range of loads than a series generator.
Therefore, the long shunt compound generator is the best type of DC generator for charging automobile batteries.