Definition: You are given a question on high school macroeconomics. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: Which of the following shifts the production possibilities frontier outward?
(A)A decrease in the price level. (B)An increase in labor productivity. (C)An increase in the money supply. (D)A decrease in the unemployment rate.

B