A unit of comparison that would be applicable to agricultural farmland or larger rural residential tracts is known as what?

The correct choice is price per acre because it is a standard unit of comparison specifically used in valuing agricultural farmland and larger rural residential tracts. In the context of real estate, especially for properties like agricultural land, acreage is a more relevant measure than square footage, as farmland is typically expansive and its value is often assessed based on the total amount of land available for cultivation or development.

Using price per acre gives a clearer understanding of the land's market value and allows appraisers to compare various properties more effectively within similar geographic and functional contexts. It's a convention in the industry that aligns better with how these larger plots of land are bought, sold, and assessed, as they are not generally subdivided into smaller measurements like square feet.

Other options, such as price per square foot, tend to be more applicable to urban residential or commercial properties where space is limited and sold in smaller parcels. Market value refers to the estimated amount for which a property should exchange on the market, but it doesn't specify a comparative unit. Cost per hectare is a measurement used primarily in metric countries, not typically relevant in the context of U.S. agricultural appraisals. Therefore, price per acre stands out as the most useful and relevant metric for agricultural farmland evaluation.