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    You must know elephants. They are very . They have a long trunk (鼻子). Their ears are like a fan. Elephants can very fast. Can an elephant jump? The answer is . It's because an elephant is too heavy. Another reason is that the bones (骨头) in an elephant's feet are closely packed together (紧紧包裹在一起). This makes an elephant not have the flexibility (韧性) to . But elephants can carry a lot of things. They are .