Which of the following settlement types is the largest size?

Megalopolis is the largest settlement type among the options given. A megalopolis is a vast urban region that comprises several metropolitan areas that are physically and economically linked. It is also known as a "super city" or "conurbation." A megalopolis typically includes multiple cities and their surrounding suburbs and towns, which are connected by highways, railroads, and other forms of transportation. These urban regions can cover vast areas and have large populations, with millions of people living within them. Examples of megalopolises around the world include the Northeast megalopolis in the United States, the Pearl River Delta in China, and the Tokyo-Yokohama megalopolis in Japan. In summary, megalopolis is the largest settlement type among the options given, as it comprises multiple metropolitan areas and has a vast geographical area and population.