The GDP deflator is a measure of the level of prices of all new, domestically produced, final goods and services in an economy. In the base year, the GDP deflator is always equal to 1 (or 100 if expressed as an index number).
This is because the base year serves as a reference point for comparing prices in other years. In the base year, the nominal GDP (which is measured in current prices) and the real GDP (which is measured in constant prices) are the same. Therefore, the GDP deflator, which is calculated as (Nominal GDP / Real GDP) × 100, will be 100 in the base year. When expressed as a ratio, it simplifies to 1.
So, the correct answer is a) 1.