Explanation:

- Option:1, Education

- Education is crucial for societal development and has been underfunded in many regions. Investment can improve infrastructure, access, and quality of education.

- Option:2, Health

- The health sector is vital for ensuring a healthy population. Investments can enhance healthcare systems, provide better facilities, and support public health initiatives.

- Option:3, Both a and b

- Education and health are both essential for a country's progress. They require significant investment to ensure a well-educated and healthy population, which in turn drives economic growth.

- Option:4, None of these

- This option suggests neither sector needs investment, which is not a valid perspective considering current global needs.

Answer: Option 3 is correct.