In the year 1840, who would most likely say, “i believe the most important cause is each boy and girl receive a good education.” select the best answer from the choices provided. joseph smith horace mann dorothea dix richard allen

To analyze this question, we need to take a few things into account: The time period, the theme of the quote, and what the people did. For the time period, we know that it's 1840. Andrew Jackson is 4 years out of the white house, and we know two things about Andrew Jackson: He has done some really bad things to the U.S., and he sparked the first reform movement. Because the theme of the quote is education, and it says "most important cause" (which is connoted with a goal, ie reform), we can say with reasonable certainty that this question is in reference to the early to mid 19th century reformers, specifically those involved in education. For the people, let's analyze what they did:

Joseph Smith - Founded Mormonism (Religion)
Horace Mann - Spear-headed the education movement with a lengthened school year and the establishment of schools used to teach teachers how to teach (Education)
Dorothea Dix - Shed light on the atrocious conditions in mental institutions by going to every single one she could find and publishing her notes on what happened; she also was in a very high nursing position during the civil war (Nursing)
Richard Allen - Died in 1831, so he couldn't say anything during 1840

With that out of the way, it's quite obvious that Horace Mann would have said that.