remain

The last person in the world was so frightened that she froze up and would not move from her chair.
The knocking became so forceful that the last person was convinced that the door would smash open. If it did not she would be very lucky.

open

There was a young woman standing there with a broad smile across her face.

"I've been looking everywhere for you!" she said.

The last person

"The last person in the world sat in a room. There was a knock at the door. The question was: to open it or to remain seated?"