Explanation:

- Option 1: If national income rises, per capita income must also rise.

- Not always true. If national income rises but the population rises even more, per capita income may not increase.

- Option 2: If population rises, per capita income must fall.

- Incorrect. If national income rises at a faster rate than population growth, per capita income can still increase.

- Option 3: If national income rises, welfare of the people must rise.

- Not necessarily. National income growth does not guarantee improved welfare if wealth distribution is uneven.

- Option 4: None of the above.

- This is the correct answer as none of the other options is universally true.

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