Colour helps you see things. But man and some monkeys and apes（猿）are the only mammals（哺乳动物）that can see colour. ____ any other mammals such as the dog, the world looks like a black-white photo. Dogs hunt ____ by listening and smelling. Like other animals dogs ___ best when things move. The animals they hunt seem to know this. A rabbit, for example, will not move when they find that they are being hunted. Then the dog _____ not see it at all.

Birds can see colour. They need to because when they fly they need to find places to land. Colour helps them know how ___ the place is and what it is like so that they are able to ____ something they think safe. Some birds see things even ___ than man. The birds that eat bugs（虫子）can see them from far away _____ the sky. So good eyes and being able to see colours help birds ___ food and also help them find out _____ there are other animals that are dangerous to them.