The correct answer is: A. Series motor
A series motor is a type of DC motor that has the field winding and the armature winding connected in series with the power source. This means that the current flowing through the field winding is the same as the current flowing through the armature winding. This results in a high starting torque, which makes series motors ideal for applications such as cranes and hoists.
A shunt motor is a type of DC motor that has the field winding 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 results in a lower starting torque than a series motor, but a higher speed regulation.
A cumulatively compounded motor is a type of DC motor that has both a series field winding and a shunt field winding. The series field winding is connected in series with the armature winding, and the shunt field winding is connected in parallel with the armature winding. This results in a motor with a high starting torque and a good speed regulation.
A differentially compounded motor is a type of DC motor that has both a series field winding and a shunt field winding. The series field winding is connected in series with the armature winding, and the shunt field winding is connected in parallel with the armature winding. However, the shunt field winding is connected in reverse polarity to the series field winding. This results in a motor with a low starting torque and a poor speed regulation.
In conclusion, a series motor is generally preferred for cranes and hoists because it has a high starting torque.