Concept:National income is the total income earned by factors of production within a country.In developing countries, labour is the most abundant factor of production.Explanation:In developing economies, the majority of the population works for wages and salaries.Labour contributes more to national output than capital or land.Profits and rent are smaller because industrialisation and capital ownership are limited.Therefore, compensation of employees forms the largest share of national income.Answer:D. wages and salaries