Option 1, Agricultural density, refers to the ratio of farmers to the total amount of arable land (land suitable for agriculture).

Option 2, Arithmetic density, is the total number of people divided by the total land area. It doesn`t take into account whether the land is arable or not.

Option 3, Physiological density, is the correct answer. This term refers specifically to the number of people per unit area of arable land. This is an important measure to understand the pressure on the productive land.

Option 4, Economic density, isn`t a typical term in geography. It might refer to the economic productivity of a certain area, but it doesn`t directly relate to population density or land utilization.