The correct answer is D. All of the choices.
Keynes emphasized that there is no automatic adjustment back to full employment in the economy, which means that any deviation from full employment can persist for an indefinite period of time. This can lead to a number of different consequences, including a lower equilibrium GDP than full employment, the occurrence of a recession, and the persistence of cyclical unemployment.
In other words, without government intervention, the economy may not naturally return to full employment, and there may be a need for policy measures to stimulate demand and create jobs. Keynes advocated for government spending and other policy tools to help stabilize the economy and promote full employment.