1 . The World’s Most Amazing Caves
Humans have been drawn to caves for thousands of years. Here are four of the world’s biggest caves.
Son Doong Cave, Vietnam
Son Doong Cave in the remote(偏远的)forests of Vietnam holds the title of the largest cave in the world. Son Doong is a spreading network of tunnels and caves, the largest of which could contain an entire New York City block with 40-story buildings. Parts of the cave’s top have fallen down，creating vast skylights that allow life to grow to a height of hundreds of feet beneath the forest floor.
Mammoth Cave, Kentucky, the United States
Mammoth Cave in Kentucky is the longest cave system in the world, with 426 miles explored—and scientists guess another 600 miles have yet to be discovered based on measurements of air movement within the caves. Mammoth Cave has drawn visitors since the 1800s, and 10 miles of underground passages are accessible to tourists today.
Sac Actun. Mexico
The longest underwater cave system in the world, Sac Actun winds(蜿蜒)more than 215 miles under Mexico’s Yucatan Peninsula. Adventurers can take a drop in the Sac Actun system through more than 248 cenotes(天然井)—the natural swimming pools that form when sinkholes connect the surface to the underwater caves.
Veryovkina Cave, Abkhazia, Georgia
Veryovkina Cave is the deepest cave in the world, spreading 1.4 miles beneath the surface. It takes professionals a week to make a round journey to Veryovkina Cave, They have to brave waterfalls, tight presses and sharp drops. But the payoff is excellent—Veryovkina
Cave’s end is a beautiful blue lake about 50 feet long and 25 feet wide surrounded by black black rocks.
1. What is special about Son Doong Cave?| A．It lies far away from the forests. | B．It has some tall plants growing. |
| C．It is the longest cave in Vietnam. | D．It is the highest cave in the world. |
| A．They end up with beautiful lakes. | B．They attract few adventurers. |
| C．They stay unexplored at present. | D．They have long cave systems. |
| A．Half a week. | B．Two weeks. |
| C．One week. | D．Over two weeks. |
