I'm trying to learn about the industry and have a few questions about market makers. I'm particularly interested in exchange specialists that provide liquidity. I'd assume the rules are different for each exchange so if possible relate it to the CBOE but if you can't, that's fine. -For each security, generally how many exchange specialists are there? I guess I am wondering if normally there are multiple market makers for one option or is there usually only one official firm? -What are the rules for market makers when it comes to setting bid/ask prices? Do they have to give the best price or can they set any price they want? If they can set any price they want, what if they set a price too far away from the market equilibrium? -Since they are market makers, do they have to hold some of the assets in inventory so that they can sell if necessary? If so, how much of it do they need to have? So for example, if I make markets for options for Citi stock, do I need to have some options in inventory? Do I also need to have Citi stocks in inventory in case I decide to sell call options? Thanks.