Where fuses are used for motor overload protection, a fuse shall be inserted in each ungrounded conductor and also in the grounded conductor if the supply system is ______ A/C with one conductor grounded.

The appropriate answer emphasizes that in a three-wire A/C supply system, one conductor is grounded, and additional safety measures are necessary to protect the motor against overload conditions. When a fuse is used for motor overload protection in this type of system, inserting a fuse in each ungrounded conductor and in the grounded conductor is crucial to ensure that both phases and the ground return path are protected.

In a three-wire A/C system, there are typically two hot conductors and one grounded conductor (which serves as a neutral). By placing a fuse in each ungrounded conductor, the system ensures that if an overload occurs, the flow of current can be interrupted appropriately, thus safeguarding the motor and reducing the risk of damage or fire. Including a fuse in the grounded conductor further enhances safety by ensuring that a fault condition does not lead to unmanageable current flow.

In contrast, options like two-wire systems might not have the same level of complexity or the need for additional protection, whereas four-wire systems are often more complex and commonly used in different configurations that might require different protection methods. Therefore, the three-wire A/C system aligns perfectly with the requirement of placing fuses in both ungrounded and grounded conductors for effective overload protection.