Explanation:

- Correct Answer: Option 2, Kahn

- Kahn introduced the employment multiplier concept. He explained how an initial increase in spending leads to a more than proportionate increase in employment.

- Option 1: Keynes

- Known for his work on economic theories. He developed the idea of the fiscal multiplier, closely related to Kahn's work but different in focus.

- Option 3: Hansen

- He was a Keynesian economist but didn't propound the employment multiplier theory. Known for promoting Keynesian ideas in the U.S.

- Option 4: Marshall

- An economist known for his contributions to microeconomics, not specifically for employment multiplier.