The correct answer is: D. Battery operated motor
A battery operated motor is preferred for operation in highly explosive atmosphere because it does not produce sparks or heat, which can ignite the atmosphere.
A series motor is a type of electric motor that has its field windings and armature windings connected in series with the power source. This type of motor is known for its high starting torque and speed regulation, but it also produces sparks and heat, which makes it unsuitable for use in highly explosive atmospheres.
A shunt motor is a type of electric motor that has its field windings connected in parallel with the armature windings. This type of motor is known for its smooth operation and constant speed, but it also produces sparks and heat, which makes it unsuitable for use in highly explosive atmospheres.
An air motor is a type of electric motor that uses compressed air to turn a rotor. This type of motor is not as common as other types of motors, but it has the advantage of being explosion-proof.
A battery operated motor is a type of electric motor that is powered by a battery. This type of motor is the most common type of motor for use in highly explosive atmospheres because it does not produce sparks or heat.