What is the maximum distance from the floor that nonmetallic surface extensions may be installed?

Nonmetallic surface extensions, such as those made from materials like PVC or other types of nonmetallic conduit or raceway, are typically used in specific applications, particularly when it comes to accessibility, safety, and compliance with electrical code requirements. The maximum distance that these extensions may be installed from the finished floor is determined to ensure that they do not pose a trip hazard and remain within a reach that is practical for users.

In this context, the correct answer highlights that nonmetallic surface extensions must be installed no more than 2 inches from the floor. This limitation is set to prevent issues associated with physical damage to the extension and ensure that the installation remains within sensible reach by users, providing a safe and functional electrical system.

The other possible distances provided in the options exceed what is considered safe and practical according to electrical codes and best practices. The 4-inch, 6-inch, and 10-inch options would likely lead to increased risk of damage to the extensions, as they would be more exposed to foot traffic and other potential hazards in typical settings. Thus, adhering to the 2-inch maximum helps uphold safety standards and functionality in electrical installations.