How Did John Maynard Keynes Explain the Great Depression, and What

How did John Maynard Keynes explain the Great Depression, and what did he suggest?

A) Keynes explained that a market-clearing equilibrium would happen eventually; he suggested providing financial help to those who needed it and then waiting for the market to self-correct.
B) Keynes came up with a theory stressing many supply and demand curves within the economy.
C) Keynes explained that a market-clearing equilibrium only happens on its own in the long run; additional action was needed to get the economy out of the Depression.
D) Keynes explained the Depression as a loss of faith or optimism among businessmen; he suggested economic encouragement for businessmen to end the Great Depression.