Used as short for “opening”, as in the initial, or opening song in a tv show, regularly used in anime.
“Do you know the lyrics to the Sailor Moon op?”
Person A: *put an Instagram story of questions*
Person B: op??
Person A: *in instagram* you are so beautiful and kind
Original Poster. You'll most likely see this in an internet forum or places like reddit.
OP is wrong. I think that the dogs provide better protection to bases than cats.