Which Statement Is the Key Argument of John Maynard Keynes

Which statement is the key argument of John Maynard Keynes?

A) Government can pull an economy out of a recession by stimulating demand and creating a cycle of increased production and jobs.
B) Government regulations during economic depressions must be lifted because they destroy the already slim profit margin.
C) The economy of size shows that monopolies are the most efficient way to distribute goods throughout a national marketplace.
D) A well-functioning economy need never experience an economic downturn.
E) Government can rectify a falling economy by regulating the money supply.