Why does an increase in literacy rates often accompany an increase in per capital income?

people who have higher-paying jobs often have the time available to develop literacy skills.
developing countries have higher-than-average literacy rates, which typically leads to higher income.
people who can read and who receive an education are eligible for higher-paying jobs.
developed countries often attempt to raise low literacy rates to improve income.

An increase in literacy rates often accompany an increase in per capital income because people who can read and who receive an education are eligible for higher-paying jobs.

Option C

Explanation:

The remuneration to be paid to an individual is determined by the set of skills and professional knowledge that the individual possesses. Moreover, modern professions require work-based knowledge. The higher the education, more is the knowledge gained.

This relation of direct proportionality between education and knowledge helps individuals with more education fetch more remuneration for their work.  In general, literacy looks to be more important for one's development and nation growth economically.

well, there are a lot of places we get information about earth from. like science classes, websites, books, newspapers, etc.