I found they were all Jeju locals who entered JEINS without taking any exams

When I left/got out of the building to investigate/find where the noises were coming from/from

The windows of her apartment were all open/opened

This is the title of a newspaper article which was written by a female S. Korean reporter, who is the head of a department

He wore a mask during the entire/whole flight

What is the difference between "sat in" and "sat on"?
Do "sit in" and "sit down in" have the same meaning?
Do "sit on" and "sit down on" have the same meaning?  **