Concede what?
If you think C is going out of business you're an idiot or know little to nothing about value investing. I know this site is about trading, but a trader that thinks they're going to make all their fortune through pure trading is only fooling themselves, or just a sadist that likes making things harder than they have to be (a lot here choose to pursue the latter). I'll buy a distressed company like C anyday and just protect the position through the options markets. As a company, C will be on this planet in some form or fashion a lot longer than you and I will be my friend.
Go ahead and short it, you'll probably make a little money down to $30 or so.
C at these levels and below is a buy and hold. Believe me, I've been down this road before and it pays the bills quite adequately. Patience pays, oh forgot, that's a virtue in short supply around here with all these "Elite" traders (pikers still living in mom and dad's spare bedroom).
Good Luck!