Read the following context and choose the best option to answer the question.
Context: It 's a tiring day . I slept really late ( or early ) this morning and I could barely think right before I speak . I ' m always having this half a second lag when I talk .
Question: What may be the reason for this situation ?
Options: 
- They had done a lot of walking around that day .
 - They had stayed up late the night before .
 - They needed to drink coffee in the morning .
 - They had school all day .


They had stayed up late the night before .