Answer:
Need for a way to measure a nation's income and output.
Explanation:
The Gross Domestic Product of a nation is a unit of macroeconomic measurement that represents the amount of goods and services produced within the territory of a nation during a given period of time. Thus, the value of each of these goods and services are added together, and the numerical total of said sum thus represents the total value of production of said country during the year.
The answer is definitely A. Houses. Basing on the Demographic Transition Model (DTM), countries categorized under stage 4 are said to have a stabilized population growth in other words birth and death rates are merely low. But still gradually on increasing number. As total population increases, housing now becomes insufficient. Examples of Stage 4 countries: Brazil, China, Argentina, Singapore, U.S.