Are animals intelligent? If they are, which animals are the most intelligent? These are not 11___ questions to answer. No one is quite sure what intelligence is. We often say that intelligence means being 12___ to solve problems. Some animals seem able to do this. 13___ dogs and cats often find their way home from long distance. To do this, they have to use their 14___ . They have to remember and think. 15___ many birds find their way over long distance. too. We do not know how they do this, but we know 16___ they do not use their intelligence. They need not 17___ places and directions before making decisions. Young birds are able to make these 18___ without help as soon as they can fly. Obviously, they are 19___ with this ability. This is not intelligence. Rather, it is what we 20___ instinct (本能). Even so, we are not so sure that dogs and cats are more intelligent than birds.
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