A Production possibilities curve or Production possibilities frontier is a graph that shows the amount of production two products achieve when the given resources are efficiently utilized per unit of time. When the graph shifts outward or to the right, then the production of both products went up, but when the curve shifts to the left or inward, then the production of both products went down. Of all the options given, the only one that decreases the rate and amount of production (causing an inward shift) would be option D: "Two metalsmiths catch a viral infection and take sick days". Options A, B and C are all causes for an outward shift in the curve.
