Detailed Explanation:

Capital formation is the only factor among the given options that necessarily leads to economic growth within a country.

✅ Statement 3 – Correct: Capital formation in X (investment in physical capital like machinery, infrastructure, and human capital) directly increases the productive capacity of the economy, making growth inevitable.

❌ Statement 1 – Incorrect: Technical progress in the world economy does not guarantee growth in country X unless X adopts and implements those technologies.

❌ Statement 2 – Incorrect: Population growth in X alone does not ensure economic growth; it may even lower per capita income if not accompanied by proportionate increase in production.

❌ Statement 4 – Incorrect: Growth in world trade volume benefits country X only if it actively participates and increases its share; mere global trade expansion is insufficient.