As a failed Catholic who once taught a catechism class (do I remember that correctly?) I am quite certain that you already know the answer to that question. Therefore, I would call it another "trick question." A trick question is one that YOU know the answer to, you just want an opportunity to propagandize.
I am certain that you are aware that Catholics do NOT limit their beliefs to narrow interpretations of questionable translations of scripture.
I am seriously asking where is the ‘communion of saints’ taught ?? When I was a child it was taught simply as a fact with no explanation of the source..
I had accepted it as a fact, now wondering its source ..no trick my friend
Do unto others......