A mobile home attachment plug cap must be __ pole, __ wire, grounding type, rated __ amps.

The correct choice indicates that a mobile home attachment plug cap must be a three-pole, four-wire, grounding type, rated at 50 amps. This configuration is essential for ensuring that mobile homes can be safely connected to the electrical supply.

In a mobile home setup, a three-pole plug allows for a proper connection to the three phases of electrical service needed to operate the home's systems efficiently. The four-wire requirement includes a "ground" wire, which is crucial for safety to reduce the risk of electrical shock and to safely carry fault current back to ground. The rating of 50 amps is significant since it accommodates the higher electrical demands typically required by mobile homes, ensuring that the electrical system can handle appliances, heating, air conditioning, and other load requirements without overheating or posing safety hazards.

Understanding these specifications helps in compliance with safety codes and standards, ensuring both functionality and safety in mobile home installations.