You are given a short paragraph, a question and two choices to answer from. Choose the correct answer based on the paragraph and write the answer(not the key).

Example input: Paragraph: Many of the worlds people live with water scarcity, and that percentage will increase as populations increase and climate changes.
 Question: John's town used to have lots of water, back when there were only a few hundred people. However, now that the town holds several thousand people, the water availability is 
 Choices: A)scarce 
B)plentiful
Example output: scarce
Example explanation: Based on the information given in the paragraph, population growth will make water more scarce, so that is the correct answer.
Q: Paragraph: The more dense the medium, the slower the light moves.
 Question: A very rarefied medium will cause light to move 
 Choices: A)faster 
B)slower
A:
faster