The Green Room [ENDED] [SOLUTIONS]

Cornelius woke up and shivered - terrible smell of his former comrades in misfortune was growing so strong, that he could almost lose his consciousness. "I have to figure how to get out of here.." - was the only thought in his starved mind.

A few days ago a group of people have found themselves locked in sort of a strange apartment, or rather a basement, consisting of a few rooms. It had immured thin holes under the ceiling and illumination was allowed only by peculiar flashing dim green luminescent lamps in some of the rooms. Dim lights were creating completely oppressing atmosphere. There were carvings on the walls and stains on the floor, none of which were paid any attention in the beginning.

One by one, unfortunate participants were dying. At first it seemed, that they were dying with no reason, of some kind of poisoning or disease, but later it became apparent, that everyone now dead has been touching stains on the floor. "This is a.. Killing floor.. I don't know what is it in there, and light is too dim to see anything, but.. I.. shouldn't touch that.."

Yesterday, the last three persons tried to solve the riddle: numerous carvings on the walls were making little sense, but they should have contained the answer - a five-letter code to the big metal door in the dark end of one of the rooms. They have noticed that some of the symbols were somehow.. out of the place, and this was anything but accidental. On the door, there was a sentence: [Choose right], with the word right written with acidic lucent green paint, so that it was seen from afar.

"Right?.. We thought we were right.. but the code didn't work.. this guy in green shirt has gone completely mad and started to wreck a chaos all over the place.. not only he has touched the stains, but.. " - Cornelius threw a look on two dead bodies, lying on the floor in the dark, far away, fastened in eternal death scramble.

"What I am expected to find here? If there was a hint.."

Solution:
[Choose right] refers to choosing letters which are right from ones marked bold.
u->p, h->a, s->D, a->K, h->o

Ending of the story:

Cornelius entered the code and door opened. "Chose right! It was a hint.. from the very beginning.."
He stood on a vast grassy field under the blue sky. Sun was shining and wind was creating a gentle rustle in the thick of trees. This was the most beautiful thing he saw in his life, previously only full of concerns of his commercial office work, struggle for making money, for feeling himself as successful as everybody around.. as good as.. dead. People who wasted their lives for nothing.

"I am finally free. I will not spend a single minute on things not important to me anymore. I have a new chance to live."

And all of this is thanks to you, dear player! Congratulations on solving this puzzle