Step 1: Understanding the Concept:
The contribution of the agriculture sector to the national economy is measured as a percentage of the Gross Value Added (GVA) or GDP.
Step 3: Detailed Explanation:
Agricultural data for the year 2018-19 indicates:
1. The share of agriculture and allied sectors in the total GVA of the country was approximately 15.9% (at current prices).
2. This sector remains the largest employer in the country despite its declining percentage share in the GDP over the decades.
3. In subsequent years, this share fluctuated, reaching nearly $20\%$ during 2020-21 due to the pandemic's impact on other sectors, but for 2018-19, it was around $15-16\%$.
Step 4: Final Answer:
Among the given options, 15% is the correct statistical representation.