If a country's population pyramid has a very broad middle while the base is gradually narrowing, which near-term opportunity and long-term challenge are both possible?

Correct answer: Near-term demographic dividend and long-term labour-force decline

The governing concept is age structure and its movement through time. A very broad middle means that a large share of the population is currently in or approaching working ages. If education, health, skills and employment are adequate, this concentration can produce a demographic dividend because more workers support relatively fewer children. The gradually narrowing base means that recent birth cohorts are smaller. As the large middle-aged cohorts grow older and smaller cohorts replace them, the labour force may eventually decline and old-age dependency may rise. Thus option A correctly combines the near-term opportunity with the long-term challenge. Option B reverses the likely dependency pattern, while C and D contradict the pyramid evidence.