One of the main characteristics of a memoir is first-person narration, because a memoir is usually written by a person who has actually experienced all of those memories. A memoir is a French word meaning memory, so this is a text based on someone's memories. Also, a memoir is a blend of actual facts, things that the author has experienced throughout his or her life, and imagination used to create a mixture between a fictional and non-fictional work of art.
The answer would be “The fiat system of currency was a great improvement over the commodity and representative systems of currency.” so the answer is (b.)
