Whose work gave rise to the separate branch of economics-macroeconomics?

John Keynes

The correct answer is option 4: John Keynes

Keynesian economics, developed by John Maynard Keynes during the 1930s, revolutionized economic thought and policy by focusing on the economy as a whole rather than just individual markets. Keynesian economics provided insights into how aggregate variables such as aggregate demand, employment, and output influence the overall performance of the economy. This marked the emergence of macroeconomics as a distinct branch of economics, separate from the traditional focus on microeconomics.