Student or Learner
A small room is full of children. They are sitting on the wooden floor, close to a big oven. Its shut is open, and red light bickers upon the faces of the children. A very old granny is sitting on the bench in front of the children and telling stories.
In this abstract I have written those articles which I felt were correct here. Still I do not know why I want to put the before wooden floor while I put a before big oven. Help me, please!
We know a room must have a floor. Therefore, they are sitting on THE floor, which happens to be wooden.
We don't know that there is an oven (do you mean "stove"?) in the room, so you need an "a" there. It's the same with "a bench."
You can refer to "the" floor, roof, walls, of a room - all rooms have them. You need an "a" for objects that are not necessarily part of any room.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.