The answer is knight to G6 and the taking the rook.
The thing is if i go to C6 i still get the discover check but i can then get their queen, and a queen is better then a rook, even i know that. I can see that my knight can then be taken though.
So the question is why is a taking a rook and keeping you knight (=-5) better the taking their queen and losing your knight (-10+3= - 7). Clearly on a point for point basis my C6 move is better the the G6 move.
So the answer must be that taking the rook and leaving their queen is beneficial for your game position. So what makes the position so good that makes me want to lose the opportunity of taking their queen? ¯\_(ツ)_/¯