[originaltext] How can a creature weighing over 5 tons and normally taking 1

How can a creature weighing over 5 tons and normally taking 150 kilograms of food and 120 liters of water per day survive in a desert environment? In the southwest African country of Namibia, and the Sahara lands of Mali further north, the desert elephant does just that.
    Although not regarded as a separate species from the African elephant, the desert cousin differs in many ways. Their bodies are smaller, to absorb less heat, and their feet are larger for easier walking across sandy surfaces. They are taller, to reach higher branches. They have shorter tusks, and most importantly, longer trunks to dig for water in riverbeds.
    Desert elephants can travel over 70 kilometers in search for feeding grounds and waterholes, and have a larger group of families. They drink only every 3 to 4 days, and can store water in a "bag" at the back of their throat, which is only used when badly needed. Desert elephants are careful feeders — they seldom root up trees and break fewer branches, and thus maintain what little food sources are available. Young elephants may even eat the dung of the female leader of a     group when facing food shortage.
    During drought they are unlikely to give birth to their young but with good rains the birthrate will increase greatly. Desert elephants have sand baths, sometimes adding their own urine to make them muddy!
    As we continue to overheat our weak planet, it can only be hoped that other animal species will adapt as extraordinarily well to change as the desert elephant.
Questions 26 to 28 are based on the passage you have just heard.
26. Why are desert elephants called careful feeders?
27. With what does the author answer the question raised in the beginning of the passage?
28. What can be inferred from the end of the passage?