Concept:A continuous built-up zone formed when towns and cities grow into each other while each centre keeps its own separate identity.Explanation:When neighbouring towns and cities expand and merge, the combined built-up area is known as a conurbation.Even though the settlements join physically, each town or city still retains its individual character and administrative identity.This term does not describe a single town, a pair of towns, or just the business area of a city.Answer:D. conurbation