The correct answer is: D. None of the above
If the prices increase by 100% over the previous year and GNP is constant, it means that we cannot determine whether production has increased, decreased, or stayed the same. This is because GNP is a measure of the total market value of all final goods and services produced in a country in a given year, while prices are a measure of the average level of prices of goods and services in a country in a given year. Therefore, if prices increase by 100%, it could mean that production has increased, but prices have also increased, so the total value of production may not have changed. Alternatively, it could mean that production has decreased, but prices have also decreased, so the total value of production may not have changed. Or, it could mean that production has stayed the same, but prices have increased.
To determine whether production has increased, decreased, or stayed the same, we would need to know more information, such as the quantity of goods and services produced.