The Huge Jump in Depository Institutions' Reserves at the Fed

The huge jump in depository institutions' reserves at the Fed in recent years can be attributed to _____

A) the Fed paying a small amount of interest on its excess bank reserves.
B) the Fed charging a small amount of interest on its excess bank reserves.
C) the Fed purchasing securities from the banks.
D) the banks feeling insecure about creating new loans.
E) the uncertainty of banks about their ability to manage their funds.