Katja Is Listening to a Lecture Late on a Friday

Katja is listening to a lecture late on a Friday afternoon.She starts to feel drowsy,and then falls into a light sleep.Which shift would be observed if her brain wave patterns were being monitored

A)  theta waves to beta waves and finally to alpha waves 
B)  beta waves to theta waves and finally to alpha waves 
C)  alpha waves to beta waves and finally to delta waves 
D)  beta waves to alpha waves and finally to theta waves