Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

Which of the following changes is most likelyto increase the overall level of supply in the long run?
Option A:A decline in the population.
Option B:An increase in productivity.
Option C:The limitation of natural resources.

Answer: B