Concept:On a flow-line map, the volume of traffic between two centres is read by counting the flow lines and applying the given scale.Explanation:Look at the map between IZABU and Ashama.Count every line drawn between these two towns.There are 8 flow lines in total.The scale in the diagram says that 1 line represents 1,500 persons.So, the total number of passengers is obtained by multiplying the number of lines by the persons per line.Thus, 8×1,500=12,000.Always include the correct unit: passengers.Answer:D. 12,000.