Final answer:
According to the NEC, live parts must be guarded from the public by permanent partitions, by elevation, or within certain buildings like dwellings, hotels, and office buildings, but not explicitly by fireproof curtains. The correct answer is D.
Step-by-step explanation:
The National Electrical Code (NEC) outlines various methods by which live parts must be guarded to protect the public. According to the NEC, live parts are guarded from the public in the following methods except: protected by fireproof curtain. The NEC does mandate that live parts be guarded using measures such as:
- By suitable permanent, substantial partitions.
- By elevation of 8 feet above the floor.
- Within dwellings units, hotels, and office buildings, where access to live parts is restricted to qualified personnel.
However, there is no NEC requirement stating that live parts must be protected by a fireproof curtain as a form of guarding. Electrical safety systems like circuit breakers and fuses are used to prevent thermal hazards. Furthermore, a three-wire system is commonly used to guard against thermal and shock hazards.