One of the lessons from the 2007-2009 financial crisis regarding the management of risk by financial institution is that:
选项：

A: many banks lacked real-time information that would allow them to assess their various risk exposures at the bank-wide level.
B: some banks, especially large ones, overestimated the trading risk associated with mortgage backed securities.
C: banks were holding too much capital as a protection against market risk.
D: many of the usual mechanisms for managing liquidity risk actually worked pretty well.