Passage One
Many animals have an excellent sense of smell, which they use in hunting. On the other hand, their eyesight may be poor. Dogs, for example, have poor eyesight and no color vision. They see only shades of gray. But the dog’s sense of smell is extraordinary,
The kind of dog known as Alsatian has 220 million olfactory (嗅觉) cells. Man has five million. Scientists believe that the Alsatian is one million times better than man in finding out odors.
The human sense of smell, however, is really quite good. The average human being can distinguish more than 10 000 different odors.
Text 1
Only two animals have entered the human household otherwise than as prisoners and become domesticated by other means than those of enforced servilities: the dog and the cat. Two things they have in common, namely, that both belong to the order of carnivores and both serve man in their capacity of hunters.
In all other characteristics, above all in the manner of their association with man, they are as different as the night from the day. There is no domestic animal which has so rapidly altered its whole way of living, indeed its whole sphere of interests, that has become domestic in so true a sense as the dog; and there is no animal that, in the course of its century old association with man, has altered so little as the cat. There is some truth in the assertion that the cat, with the exception of a few luxury breeds, such as Angoras, Persians and Siamese, is no domestic animal but a completely wild being. Maintaining its full independence it has take
A. people can use them for hunting
B. they are associated with man closely
C. they have the same way of living
D. they are equally liked by people
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