请教GWD6-Q12

lanpingzhen

我觉得ABE好像都对啊，请NN指教~~（正确答案是A）谢谢啦

GWD6-Q12:

Which of the following is mentioned in the passage as a way in which brown bears and sloth bears are similar?

A.    They tend to become aggressive when provoked.

B.    They live almost exclusively in treeless environments.

C.    They are preyed upon by animals that can climb or topple trees.

D.    They are inefficient in their locomotion.

E.     They have relatively large canine teeth.

这是文章

The sloth bear, an insect-eating animal native to Nepal, exhibits only one behavior that is truly distinct from that of other bear species:  the females carry their cubs (at least part-time) until the cubs are about nine months old, even though the cubs can walk on their own at six months.  Cub-carrying also occurs among some other myrmecophagous (ant-eating) mammals; therefore, one explanation is that cub-carrying is necessitated by myrmecophagy, since myrmecophagy entails a low metabolic rate and high energy expenditure in walking between food patches.  However, although polar bears’ locomotion is similarly inefficient, polar bear cubs walk along with their mother.  Furthermore, the daily movements of sloth bears and American black bears which are similar in size to sloth bears and have similar-sized home ranges reveal similar travel rates and distances, suggesting that if black bear cubs are able to (26) keep up with their mother, so too should sloth bear cubs.
                    

      An alternative explanation is defense from predation.  Black bear cubs use trees for defense, whereas brown bears and polar bears, which regularly inhabit treeless environments, rely on aggression to protect their cubs.  Like brown bears and polar bears (and unlike other myrmecophagous mammals, which are noted for their passivity), sloth bears are easily provoked to aggression. Sloth bears also have relatively large canine teeth, which appear to be more functional for fighting than for foraging.  Like brown bears and polar bears, sloth bears may have evolved in an environment with few trees.  They are especially attracted to food-rich grasslands; although few grasslands persist today on the Indian subcontinent, this type of habitat was once wide spread there.  Grasslands support high densities of tigers, which fight and sometimes kill sloth bears; sloth bears also coexist with and have been killed by tree-climbing leopards, (52) and are often confronted and chased by rhinoceroses and elephants, which can topple trees (53).
                    Collectively these factors probably selected against tree-climbing as a defensive strategy for sloth bear cubs. Because sloth bears are smaller than brown and polar bears and are under greater threat from dangerous animals, they may have adopted the extra precaution of carrying their cubs.  Although cub-carrying may also be adoptive for myrmecophagous foraging, the behavior of sloth bear cubs, which climb on their mother’s back at the first sign of danger, suggests that predation was a key stimulus.

xiaowanwan

B中的exclusive treeless两个词语同样是否定，双重否定，所以错误。

xiruiming

这句话主要讲的是sloth吧 而A定位后 比较的对象才正确啦

franker

Like brown bears and polar bears, sloth bears may have evolved in an environment with few trees. 

请解释B选项

lanpingzhen

非常感谢~~

bobiouous

lz主要看个几遍把特征和各种不同的熊对应起来就可以得出正确答案了。

A)正确。 出处：Like brown bears and polar bears (and unlike other myrmecophagous mammals, which are noted for their passivity), sloth bears are easily provoked to aggression.

B)根据Black bear cubs use trees for defense, whereas brown bears and polar bears, which regularly inhabit treeless environments, rely on aggression to protect their cubs.这里类比的是brown bear和polar bear。

C)从文中只看到sloth bear有被会爬树或者推倒树能力的动物捕猎。根据我们常识也能知道豹子一般都不敢惹棕熊的

D)同样inefficient in their locomotion的是sloth bear, American black bear和polar bear。这里从文章第一段看出

E)文中只提到sloth bears有较大的canine teeth。根据这句话Sloth bears also have relatively large canine teeth, which appear to be more functional for fighting than for foraging.

这句话可能有些让人误解为sloth bear也居住在treeless environment里：Like brown bears and polar bears, sloth bears may have evolved in an environment with few trees. 但是我们可以看到这句话是讲evolve而不是inhabit/live，所以不能那么认为。