• Physiological Zero in Embryology:
• The physiological zero temperature for avian eggs is defined as the temperature below which embryonic cell division (blastoderm development) is suspended in physiological arrest:

• Hatching eggs awaiting incubation are stored at $15 - 18^\circ\text{C}$ (well below physiological zero) to maintain dormancy. If eggs are stored between physiological zero ($24^\circ\text{C}$) and incubator temperature ($37.5^\circ\text{C}$), abnormal embryonic development occurs, causing early embryonic mortality.
• nalysis:
• (24 °C): Correct standard physiological zero temperature.

Correct option: (3) 24°C