At what temperature will interim power deactivate in the nacelle?

The correct answer is 70°. Interim power in the nacelle is designed to deactivate at this temperature to prevent overheating and potential damage to the aircraft's systems. This safeguard is essential for maintaining operational safety and integrity, ensuring that the equipment remains within its safe operating limits.

In the context of the other temperature options, each represents a threshold that could potentially lead to unwanted operational risks. For instance, if interim power were to deactivate at a higher temperature, it could allow conditions that might lead to overheating or system failures. Thus, 70° serves as a well-considered limit to balance operational needs with the safety of the equipment.