Read the selection. Then, answer the question(s). (1) The most catastrophic natural disaster in the United States was a Category 4, or extreme, hurricane that struck Galveston, Texas, on September 8, 1900. (2) A 15-foot storm surge killed more than 8,000 people on the low-lying island. (3) In an effort to prevent a similar disaster in the future, the island's elevation was raised farther above sea level. (4) Workers also constructed a sea wall to try to protect the city. Which sentence gives the main idea of the selection?