Which of the following best describes the purpose of raising and lowering the
required reserve ratio?

It is used by Fed to manage the economy by increasing or decreasing the amount of loans being made

Explanation:

The Fed decides on required reserve ratio for the banks and other financial institutions; t can lower or raise it. Reserve ratio is the portion of all the money that bank are required  to sets aside and hold onto; this means they are not allowed to lend that out to borrowers. This is a technique that is used to control the supply of money in the economy. By decreasing this ratio, banks will have more money to lend out and vice versa.

answer; is usually (less than) the socially optimal level of consumption;