A、A very popular food plant. B、A plant with limited uses. C、A food plant which has been used. D、A plant used as a main food. D文中

(26) One of the reasons for our success as a species is our ability to eat and thrive on a large variety of foods. Many animal species have become extinct or are on the verge of extinction partly because they lack this adaptability. They need to feed on particular plant food or a particular kind of animal or insect. If this source of food is for any reason removed, then the animal concerned is unable to change to a different diet. Gradually it becomes extinct. We know that many animal species have died out, but so have some human species such as the early form of man that is called Neanderthal man. (27) Perhaps part of the reason for his failure to survive was his lack of adaptability in diet. Modern humans are almost entirely free from the limitation of any particular food requirements. We are able to survive on a wide variety of foods including both animals and vegetables. For example, the Eskimos are almost totally meat eaters: seal, bear, whale meat and fish form their whole diet, the Aborigines of Australia, living in arid desert regions, have learnt to survive by making use of forms of insect life as food to supplement their diet of wild fruits and roots. Men have learnt to survive in the deserts and dense rain forests, raise domesticated animals living at high altitudes so as to inhabit the mountainous regions like Tibet. (28) In Pacific islands, people have made the coconut their chief food.