If the labour force of a country is 2.5 million and 2 million are employed , what is the unemployment rate?

The unemployment rate is the percentage of the labor force that is unemployed and actively seeking employment. In this case, the labor force is 2.5 million and the number of employed people is 2 million. Therefore, the number of unemployed people is 2.5 million - 2 million = 0.5 million. To calculate the unemployment rate, we divide the number of unemployed people by the labor force and multiply by 100 to express the result as a percentage. So, the unemployment rate is (0.5 million / 2.5 million) * 100 = 20%. Therefore, the correct option is: 20%.