Dolphins are our friends. They can use tools to solve problems although they don't have hands.   For example, scientists have ever found that a dolphin can make a shy eel  come out of its hole with a dead fish. Dolphins use different sounds to exchange information with each other. Scientists in Hawaii have developed a sign language to give instructions to dolphins, and the results are amazing. They find that dolphins not only understand the meaning of individual   words, but also understand the importance of word order in a sentence. Most animals enjoy playing -- but dolphins seem to like making their games as challenging as possible. On a beautiful day in 1997, scientists at a beach watched a little dog going into the sea and swimming towards the dolphins. To their surprise, the dolphins came up to the dog and then started throwing it into the air. The dog seemed to enjoy the "game" and continued playing with the dolphins for more than an hour. Dolphins live in a very different world from ours, but they are very good at our "IQ tests" . For example, they will jump out of the water when they hear a whistle   noise. They do this because they will get a fish as a prize. There is still much to learn about these cute problem-solvers, but it is certain that watching a dolphin show is fun. ,. (5) Why do the dolphins jump out of the water when they hear a whistle noise?
Because they want to get a fish as a prize. Because they enjoy playing on the water. Because they want to play with other dolphins. Because the dolphin keepers want them to come out.