It's (a). If you get substantial food while you were starving, your body will guess that this time of the day is a good one to be awake at, in case the food sou

It's (a). If you get substantial food while you were starving, your body will guess that this time of the day is a good one to be awake at, in case the food source is available every day at the same time. So a solid breakfast after a short period of fast resets the internal clock.