听力原文：M: Hi, Cathy. I am here because I visited caves all over North America. Since you are going to study cave formations, Dr. Bow asked me to come to share some of my experiences with you. W: Hi, Bill. So wonderful! I can't wait to hear about it! M: Recently, I visited the La Chagire Cave in New Mexico, my dream has always been to discover a new passage way. I had a chance there, because La Chagire is so large that discoveries are frequently made there. W: Was it newly discovered? M: The cave was not even discovered until 1986. However, people in that area had figured that there must be a cave nearby, because of the strong wind that blew from behind the huge rock that covered the entrance. Enormous amount of air enter and exit the cave in order to maintain balance of the pressure with the inside air. W: You must have had to fight heavy wind when you were in the cave. M: Exactly, I had to fight 45 mile per hour winds. After all that effort, I had to be extremely careful maintaining my energy level. People who are tired tend to be careless, and may be more concerned about getting out of the cave than taking care of it. W: Anything interesting or thrilling in the cave? M: There are formations in La Chagire that look like ocean waves, Christmas trees and other stuff no one has ever seen before. W: Caves are normally created by carbonic acid, right? M: But this cave sculpted out by very powerful sulfuric acid that swells up from below. (23)