Answer: E) all banks whether or not they are members of the Federal Reserve System
Step-by-step explanation:
The Federal Reserve System requires that all banks regardless of their membership or lack thereof of the FED adhere to the reserve requirements it has established.
The Reserve Requirements are very essentially to the economy as they help control liquidity as well as protect both banks and it's customers from Bank Runs (customers withdrawing their money in massive numbers because they fear for the future of the bank).
Recently though, the FED has reduced this requirement to ZERO to enable banks borrow out more funds amidst Coronavirus concerns.