Read the passage carefully until you have got its main idea, and then select one appropriate word for each gap from the words following the passage. Behavior is the way that animals act. For example, how do they get food or take care of their young? How do they find a place to live in or _________(1) themselves from er? Much behavior is innate; that is, animals are born with it. _________(2), animals learn much other behavior. There are several kinds of learned behavior. One _________(3) of learned behavior is habituation. This happens when an animals learns to feel comfortable in a new _________(4) and doesn't pay attention to it any more. For example, young horses are often afraid of noisy streets. But after a while, they learn to pay no attention to the normal _________(5) and sounds of a city. Another kind of learned behavior is conditioning. It is a way of learning by association—that is, by putting _________(6) different ideas. In 1900, Ivan Pavlov (伊万·巴甫洛夫), a Russian biologist, studied conditioning in dogs. Dogs innately salivate (produce liquid in the mouth) when they smell food. Pavlov _________(7) a bell every time he gave food to a dog. Soon the dog started to _________(8) the sound of the bell with the smell of food. After some time, it salivated when it heard a bell alone, _________(9) food. Learning is important for all animals in a new _________(10). It allows an animal to be adaptable—that is, able to change in a new situation. without responded associate However rang aside type defend environment Anyway sights together situation way protect