What type of disconnecting means is not permitted for circuits leading to motor-fuel-dispensing equipment?

The correct choice identifies that single-pole breakers utilizing handle ties are not an acceptable disconnecting means for circuits leading to motor-fuel-dispensing equipment. This stems from the need for a reliable and safe method to disconnect the electrical supply in the context of hazardous locations such as those involving flammable liquids.

Single-pole breakers with handle ties can potentially lead to a situation where only one pole of a multi-pole circuit is de-energized. This can result in equipment that is still energized and poses a safety risk, especially in environments like fuel dispensing where the possibility of fire or explosion is a significant concern. Equipment in these areas requires a disconnecting means that ensures complete de-energization of all current-carrying conductors.

In contrast, double-throw switches and emergency stop buttons are designed to function in a manner that ensures complete disconnection from power, reducing risk in emergencies. Two-pole breakers also offer a greater level of safety by disconnecting both conductors of a circuit, which is essential in ensuring that machinery is entirely isolated from electrical power. Thus, the regulation aims to ensure that disconnecting means provide definitive protection and a safe working environment in sensitive applications like motor-fuel dispensing.