Answer:
d. education
Step-by-step explanation:
Nations develop when the workforce is qualified. This occurs through a good educational level from childhood to university. Education may be private, but not everyone can access when it needs to be paid. Thus, if a country wants to develop human capital and the workforce, it must invest in quality education. This way, a country will be able to train professionals from all areas of education, such as language, mathematics, biomedical and technological areas.