Since the Financial Crisis of 2007-2009, Borrowing at the Federal

Since the financial crisis of 2007-2009, borrowing at the federal funds rate

A) has dropped significantly because the rate has increased.
B) has replaced open-market operations as the most frequently used tool of monetary policy.
C) virtually never happens, as most banks have sufficient excess reserves.
D) has increased significantly, as banks struggle to maintain enough reserves.