Final answer:
Non-metallic sheathed cable in an attic on top of joists must be protected within 6 feet of the scuttle and fastened every 4 1/2 feet. Hence, the correct response to the inquiry is option d, which states that both a and b conditions must be met.
Step-by-step explanation:
The question pertains to electrical wiring standards concerning non-metallic sheathed cable installations in an attic, which is an important aspect of residential electrical work for safety and code compliance.
The National Electrical Code (NEC) has specific requirements for the installation of such cables. When non-metallic sheathed cable, commonly known as Romex, is run across the top of floor joists in an attic, there are two particular conditions that need to be met:
- The cable must be protected within 6 feet of the attic entrance, often referred to as a scuttle hole, which usually involves running the cable on running boards or protecting it with guard strips to prevent damage.
- Furthermore, the cable must be fastened every 4 1/2 feet at minimum to provide support and prevent it from sagging or being damaged over time.
Taking these points into account, the correct answer to the question is option d, meaning both conditions a and b must be fulfilled for proper non-metallic sheathed cable installation in an attic on top of joists.