Have you ever heard of friendships among animals? At a zoo in Germany, an (usual) friendship developed between a cat and a bear.

    One day, some (worker) in the zoo noticed a black cat was in the bear's cage (笼子), and the two animals were enjoying (they) together. The bear keeper allowed the cat (stay) with the bear. And later, the pair and their friendship became hot topic at the zoo.

    After several years, a new cage (build) for the bear. However, the cat was kept outside the cage, so it walked around (angry) and cried to be with the bear. Instead of (drive) the cat away, the bear keeper took pity on it and let it stay with the bear. The cat and the bear got closer than before. They often shared meals each other in the sun.

    This may surprise humans they usually expect animals to form relationships with others of the same species (物种). However, it may be natural for animals to have their own ideas about who would make a good friend.