Which connection can serve as a disconnecting means for fixed electric pipelines rated 20 amps or less?

The correct answer is a factory-installed attachment plug rated at 20 amps and 150 volts, as it meets the necessary specifications to serve as a disconnecting means for fixed electric pipelines rated 20 amps or less.

A disconnecting means is essential for ensuring safety, allowing for the complete disconnection of the electrical supply for maintenance or repair purposes. The rating of 20 amps is crucial because devices rated for this amperage can safely handle the current of the pipelines in question without risk of overload or failure. Additionally, the voltage rating of 150 volts indicates that the device can withstand the electrical potential present without becoming a hazard.

Using a plug specifically rated for 20 amps ensures that it is designed to handle the maximum continuous load efficiently while providing a clear and safe means of disconnection. This allows technicians to remove power from the lines easily and safely when necessary.

In contrast, the other choices either do not match the required amperage rating or voltage rating to serve effectively as a disconnecting means for fixed installations rated at 20 amps or less.