Final answer:
The NEC code reference that addresses whether you can connect the metal frame of an attic exhaust fan to the grounded conductor is 250.136(A), which generally prohibits this practice and requires grounding non-current-carrying metal parts through other means.
Step-by-step explanation:
The question relates to the National Electrical Code (NEC), which is a set of guidelines used for electrical wiring and equipment installations. Specifically, this question asks about the section of the NEC that would address the grounding requirements related to an attic exhaust fan's metal frame. The correct reference in the NEC that either permits or prohibits connecting the metal frame of the attic exhaust fan to the grounded conductor is 250.136(A). This section states that typically, non-current-carrying metal parts of fixed equipment, which are not likely to become energized, must be grounded.
Whereas, 250.142(B) and (C) deal with the use of the grounded conductor for grounding equipment in specific situations which is not typically relevant to an attic exhaust fan. 250.136(B) provides conditions under which non-current-carrying metal parts can be connected to the equipment grounding conductor. Thus, for this application, the grounded conductor should not be used as a grounding means for the fan's metal frame as per the rules provided in 250.136(A).