When the Economy Began a Downturn in 2007, One That

When the economy began a downturn in 2007, one that rapidly worsened when the global financial system came to the brink of collapse in 2008, the Federal Reserve significantly lowered the ______________ in order to boost the economy, eventually lowering it to nearly rock bottom before pushing it upwards again in 2018.

A) federal funds rate (i.e., the interest rate charged by one bank to another)
B) discount rate (i.e., the interest it charges on loans it extends to member banks)
C) reserve requirement (i.e., the amount of cash and securities that every bank must have to cover withdrawals)
D) open-market rate (i.e., the interest it charges on loans it extends to member banks)