Final Answer:
Tony was likely woken up from stage N₃ sleep.
Step-by-step explanation:
Sleep is typically divided into four stages: N₁, N₂, N₃, and REM (rapid eye movement). Each stage represents a different depth of sleep. N₃, also known as slow-wave sleep or deep sleep, is the stage where it is most challenging to wake someone up. It is characterized by slow delta waves, and transitioning from this stage to wakefulness can be a gradual process.
During N₃ sleep, the body experiences physiological changes, such as a decrease in heart rate and blood pressure. This stage is crucial for physical restoration and growth, as well as memory consolidation. When Tony received a call and took some time to fully engage in the conversation, it suggests that he was likely in a deep sleep state. The sluggish response time, the need to locate his phone, and the gradual awakening all align with the characteristics of transitioning from N₃ sleep to wakefulness.
It's important to note that the sleep cycle is not strictly linear. Individuals go through multiple sleep cycles each night, with each cycle consisting of different stages. The fact that Tony took time to fully wake up implies that he was likely in the deeper stages of sleep, such as N₃, at the time of the call. Understanding the sleep stages helps explain the variability in waking experiences and highlights the importance of considering the sleep cycle's complexity when analyzing waking responses.