The last answer, "Renaissance artists made figures look solid and lifelike by using light and shadow; figures in medieval art look flat," is the correct answer.
Winston Churchill called it this to refer the the imaginary wall <span />
Two Treatises of Government
The argument is that the mortality transition occurs exogenously and is the cause of a subsequent decline in fertility and rise in urbanization. This exogenous demographic process plays out over time, and has effects on economic, social, and political development. Hope this helps. :)
