C/D is cranial dislocation, basically breaking the rats neck. Pin the rats head to a table with a ruler or something and pull the tail to break the neck. I'm surprised the tail would come off but then again I've never tried it. I don't have the stomach for that, I'd rather let the snake do the killing lol.
On another note my snakes wound seems to have healed. I got a bottle of Betadine and now I can't even see where she got bit.