Stretching more than five kilometers (1)…………..and researching heights of 200 meters, the main carven of Hang Son Doong is large enough to house an entire New York City block. In 2013 Hang Son Doong (2)……………..to the public for the first time. The journey to Hang Son Doong is not for the faint-hearted. Involving two days of intense jungle trekking and river crossing to reach the entrance, nights are spent camping inside the cave and the nearby Hang En, now known to be the third (3)…………..cave in the world. Once inside, hikers are expected to climb, crawl and swim through underground rivers to arrive at the end of the cave. It’s an (4)…………….like no other. Despite the physical demands, guests are perfectly cared (5)………….. Two caving experts, three local guides, two chefs, two park rangers and 20 porters join (6)……………expedition. They ensure everyone’s welfare and safety, and the preservation of the cave is looked after with expert precision. 1. A. wide B. tall C. long D. big 2. A. was opened B. is opened C. was opening D. opens 3. A. large B. larger C. largest D. enlarge 4. A. adventure B. tour C. trip D. journey 5. A. off B. for C. down D. with 6. A. plenty B. few C. many D. every