D: The principle that if some people in society become rich, then eventually the poor will benefit because the wealth will trickle down to them through employment and other trade.

Many people protest that this is right-wing propaganda designed to justify exploitation. Anyone who believes that trickle-down is not real might like to consider bus drivers in New York and Cairo. Both do the same job, for similar hours, with similar conditions, and take similar risks. One of them is paid about 10 times as much as the other. Trickle-down is real.