The role of the FDIC is to

a$.$ protect the bank from downside loss by creating a hedge on its equity investments.

b$.$ reimburse depositors up to $$250,000$ in case the bank is unable to meet its obligation.

c$.$ protect the bank from downside loss on investments should an investment firm become insolvent.

d$.$ reimburse the bank for obligations owed to it by other financial institutions.