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).

Paragraph: The main law is the law of superposition. This law states that deeper rock layers are older than layers closer to the surface.
 Question: When you go into a cave, the rocks at deeper levels are _____ than the rocks on the surface. 
 Choices: A)younger 
B)older
older