Beauty in nature is the same everywhere. Nature is full of colour. Plants, animals, birds and insects have many beautiful colours. Colour, however, for animals, birds and insects is not only for beauty. It means life to them, because it helps them hide from the enemies. Birds, for example, use colour to tell other birds to stay away from their nests. They sing and move their wings to show the colour as a warning to other birds. One kind of butterfly is black. It tastes bad to birds. Once a bird eats this kind of butterfly, it remembers the bad taste. One kind of fish can change its colour to the colour of the surrounding plants and rocks. This prevents the fish’s enemies from finding and eating it. Colour is very important to nature, animals, birds and insects. It often save their lives.（）
A. To remember the bad taste. B. To show their beauty. C. To stay away from others. D. To warn other birds.