E17, S4: **Rules of engagement**

I use the part with Quark from [chakoteya transcript][1] to expose my doubts.

> [**Quark's**]
> 
> **QUARK** (to camera): It was about seventeen hundred hours. I was doing some cleanup work. Doctor Bashir was at the bar talking to
> Etheria, one of the dabo girls.
>
> **BASHIR**: Have you ever seen the wormhole open?
>
> **QUARK**: No, wait. It wasn't Etheria. It was Glidia.
>
> **BASHIR**: Have you ever seen the wormhole open?
>
> **QUARK**: Or was it Midia?
>
> **CH'POK** [**OC**]: Mister Quark, is this necessary?
>
> **QUARK**: No, no, no. It was Ralidia and she was with Morn. And he was the one who turned to her and said
> 
> [**Wardroom**]
> 
> **CH'POK**: Can we return to the matter at hand, please?
>
> **QUARK**: Oh, right. Well, as I said, I was cleaning up and I saw Mister Worf come in.
> 
> [**Quark's**]
> 
> **CH'POK** [**OC**]: Was there anything unusual about that?
>
> **QUARK**: No, he comes in here all the time. But he was in a good mood.
>
> **CH'POK** [**OC**]: And that's unusual?

The same holds true for the previous part with Dax, and the following with Mr O'Brien.

It seems there are one Quark in the wardroom, and another in an holographic room.

I don't understand:

1) The reason of this: They may simply answer the question and reconstruct verbally the dynamics of events.

2) How is it possible to address Quark in the holographic recording, while he is currently present in the wardroom?

3) What does it means the OC acronym that appears sometime next to some character's name?




  [1]: http://www.chakoteya.net/DS9/490.htm