The General Theory of John Maynard Keynes Exerted a Major

The General Theory of John Maynard Keynes exerted a major impact on macroeconomics during the 20ᵗʰ century primarily because

A) it provided the only logically consistent view of what caused the Great Depression.
B) it provided a reasonable explanation of what went wrong during the Great Depression and what could be done to prevent it from happening again.
C) it explained how gross domestic product could be measured and why this was important.
D) it derived the conditions necessary for maximum efficiency of resource use and explained how these conditions could be achieved through central planning.