Answer:
The correct answer would be, Productivity. Productivity is the most important factor that explains differences in living standards across countries.
Step-by-step explanation:
Countries are considered poor or rich on the basis of how productive they are. Productivity means the state of being productive. It is the rate of Output per unit of Input. The countries which are considered better than other countries have more unit of output on per unit of input. The productivity is generally estimated through the industries. The effectiveness of productive efforts in industries will lead a country to the top of the list of most productive countries.
For example, if a country is able to produce 1 ton of a product through an equipment and the other country is able to produce 10 tons of the same product through the equipment, it is assumed that the other country is more effective and productive than the first country.