The correct answer is (a). Underdeveloped economies are also known as primary sector economies. This is because these economies are heavily reliant on the extraction and processing of raw materials, such as agriculture, mining, and forestry. These economies tend to have low levels of industrialization and technology, and a high proportion of their population lives in rural areas.
(b) Industrial economies are economies that have a high proportion of their workforce employed in manufacturing and other secondary sector industries. These economies tend to have a high level of technology and infrastructure, and a large urban population.
(c) Advanced economies are economies that have a high level of economic development, with a high standard of living and a high level of technology. These economies tend to have a large service sector, and a small proportion of their population living in poverty.
(d) None of the above is not the correct answer.