Reading Comprehension
Directions: Read the following passage. Choose the best answer from the four choices marked A, B, C and D for each question. 

     Spelunking has been called “mountain climbing upside down in the dark”. However, this description is not entirely accurate. The mountain climber knows where he is going. He climbs a mountain because it is there. A spelunker, on the other hand, doesn’t know what is there. All he sees when he enters a wild cave is a hole in the surface of the earth — a very dark hole. Once he gets inside he may find it runs only a few hundred feet or, like one cave in Switzerland, more than 35 miles. He may find big hall, subway like tunnels, rivers or strange and beautiful limestone formations.
     Some spelunkers have become famous for their discoveries. Several years ago Norbert Castreet, a Frenchman, was exploring a cave that had a rapidly flowing underground river. He followed the river until it went under a cave wall and disappeared. Wearing a bathing suit and a rubber cap, he dived into the river. He surfaced on the other side of the cave wall and found a huge hall untouched and undisturbed for tens of thousands of years.
     My wife and I became spelunkers almost by accident. We were driving down the Pan-American Highway to Mexico City when I noticed several black openings up in the mountains near the road. I stopped and asked what they were, and learned that they were a network of large caves. Following a guide, we were climbing slowly up the mountain. When we reached the top, a large opening appeared under an overhanging cliff. Inside was a smaller hole covered by a wooden door. Taking a gasoline lamp in one hand, the guide opened the door. We followed him down the smooth cement steps. Strange shapes moved on the walls as his lamp swung back and forth at each step.
     This was a limestone cave, formed hundreds of thousands of years ago by the slow dripping of water through the cracks of the rock. The guide pointed out formations that looked like horses, tigers, hands and plants.
     When we left the cave about an hour later, we saw a sign mentioning the National Speleological Society. Our interest awakened, we noted the address and wrote for further information. The reply informed that there were “grottoes”, local chapter of the society, all over the United States. We joined one that was near our home. Soon we were making our first trip through a wild, unmapped cave. That was 12 years ago. Since then I have explored caves in Europe, Central and South America, and all over the United States.