单选题
Shark Attack!
Craig Rogers was sitting on his surfboard, scanning the distance for his next wave, when his board suddenly stopped moving. He looked down and was terrified to see a great white shark biting the front of his board. "I could have touched its eye with my elbow," says Craig. The shark had surfaced so quietly that he hadn"t heard a thing.
In his horror and confusion, he waved his arms and accidentally cut two of his fingers on the shark"s teeth. He then slid off the opposite side of his surfboard into the water. Then, with Craig in the water and blood flowing from his fingers, the five-meter-long shark simply swam away, disappearing into the water below.
Although sharks are often categorized as killers that hunt and eat as many humans as they can, this is factually inaccurate. Sharks very rarely kill humans. A person has a greater chance of being struck by lightning or drowning in a bath than of being killed by a shark. Only 74 people have been reported killed by great whites in the last century. But great white sharks can reach six meters in length and weigh 2,200 kilograms or more. With frightening jaws that can hold up to 3,000 teeth arranged in several rows, they could very easily kill and eat a helpless human in the water. Why is it, then, that most people survive attacks by great whites? Shark researchers are trying to comprehend the reasons that allow people to escape without being eaten.
The most common explanation is that great whites don"t see well. It has been thought that they mistake people for the seals or sea lions which make up a large part of their diet. There is reason to doubt this, however. Recent information shows that great whites can actually see very well. Also, when attacking seals, great whites shoot up to the surface and bite with great force. When approaching humans, however, they most often move in slowly and bite less hard. They soon discover that humans are not a high-fat meal. "They spit us out because we"re too bony," says Aidan Martin, director of Reef Quest Center for Shark Research.
Shark researchers like Martin hypothesize that great whites are actually curious animals that like to investigate things. It"s possible that they use their bite not only to kill and eat, but also to gather information. Although such an experience is unlucky for people like Craig Rogers, when sharks bite surfboards or other objects or people, they are likely just trying to learn what they are.