The correct answer is: A. Tower wagon.
A tower wagon is a self-propelled vehicle that is used for repairs in overhead power lines. It is equipped with a ladder that can be extended to reach high-voltage lines. The tower wagon also has a platform that can be used to stand on while working on the lines.
A ladder trolley is a device that is used to transport ladders. It is typically mounted on a truck or trailer and can be used to move ladders to different locations. Ladder trolleys are not equipped with platforms or other features that make them suitable for use in overhead power lines.
A moped trolley is a type of cart that is powered by a moped engine. It is typically used to transport goods or materials over short distances. Moped trolleys are not equipped with ladders or platforms and are not suitable for use in overhead power lines.
Therefore, the correct answer is A. Tower wagon.