The standard of living refers to the level of wealth, comfort, material goods, and necessities available to individuals in a society. 
It is best reflected through per capita income, which is the average income earned per person in a country. 
Per capita income is calculated as: National Income divided by the total population. 
This gives a clearer picture of how prosperous or developed a country is from the citizens’ perspective. 
Now let’s evaluate the options: 
(A) Poverty ratio — Measures the percentage of population below the poverty line, not overall living standards. ❌ 
(B) Per capita income — ✔️ Correct. It best represents the average standard of living of individuals in a country. ✅ 
(C) National income — Does not consider the population size; therefore, it is not a good indicator of living standards. ❌ 
(D) Unemployment rate — Indicates employment health but not comprehensive living conditions. ❌ 
Thus, the correct answer is option (B).