Final answer:
Melissa's disorientation and lack of awareness upon waking to a car alarm suggest she was in stage 3 sleep, which is characterized by delta waves and is a deep sleep phase from which it's difficult to awaken.
Step-by-step explanation:
A car alarm wakes Melissa up at 1:30 am, and since she is disoriented with no idea what time it is or what's going on, it is likely that she was in stage 3 sleep. This stage is referred to as deep sleep or slow-wave sleep, characterized by low frequency, high amplitude delta waves. It is during this time that a person's heart rate and respiration slow down, and more importantly, it is much more difficult to awaken someone from sleep during stage 3 than during earlier stages. The disorientation Melissa experienced could be attributable to the abrupt transition from the deep sleep of stage 3, where brain activity is at its lowest, to full wakefulness, caused by the disruptive car alarm.
Melissa was probably in stage 1 sleep when the car alarm woke her up. Stage 1 sleep is a transitional phase between wakefulness and sleep, characterized by alpha and theta brain waves. Alpha waves are associated with relaxation, while theta waves are even lower in frequency and higher in amplitude. People in stage 1 sleep can be easily awakened and may not feel like they have been asleep if woken up during this stage.