"S" loops in equipment direct burial ______ to raceway transitions, expansion fittings in raceway risers to fixed equipment, and generally, the provision of flexible connections to equipment subject to settlement or frost heaves are recognized by the NEC.

The reference to "S" loops in equipment direct burial focuses on the flexibility and movement required in certain wiring installations, specifically in coping with physical changes in the environment, such as settlement or frost heaves. The use of flexible connections is essential in these scenarios to prevent damage to the wiring from movement caused by these factors.

Cables and conductors are the correct context as they encompass the types of wiring being installed and utilized in these loops and transitions. The NEC (National Electrical Code) recognizes the importance of adequately accommodating movement and protection in these situations. It's specifically through the properties of cables and conductors that one can manage the physical demands placed on them during environmental changes.

To elaborate, feeders and circuits typically refer to broader electrical paths rather than specifics about installation techniques and provisions in scenarios involving movement. Sideways and cable trays represent different components of electrical distribution and management rather than the specific focus on flexibility and protection in relation to environmental changes. The answer "none of these" would not be appropriate since cables and conductors are indeed integral in discussions about wiring methods when addressing the unique challenges posed by direct burial and transitions.