There was talk in 2008 (because of the subprime mortgage financial crisis) of the US government investing in private banks as a way to get additional cash into the banking systems. If you are think the cash infusion is a good idea, but you are very concerned about the government taking over control of the banking system, you would prefer that the government
purchase common stock in the primary market
purchase common stock in the secondary market
purchase preferred stock in the primary market
purchase preferred stock in the secondary market