$20.$ A a$.$ b$.$ c$.$ d$.$

buys government bonds, and in so doing increases the money supply. buys government bonds, and in so doing decreases the money supply. sells government bonds, and in so doing increases the money supply. sells government bonds, and in so doing decreases the money supply.

bank$$s reserve ratio is $10$ percent and the bank has $$2,000$ in deposits. Its reserves amount to $$20.$

$$200.$ $$400.$ $$1,800.$