那位NN指点一下？

crbeijing

GWD-6-Q9 to Q12:

      The sloth bear, an insect-eating

      animal native to Nepal, exhibits only one

      behavior that is truly distinct from that of

Line     other bear species:  the females carry

  (5)    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

(10)   (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

(15)   walking between food patches.  How-

ever, although polar bears’ locomotion

is similarly inefficient, polar bear cubs

walk along with their mother.  Further-

more, the daily movements of sloth

(20)   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

(25)   able to 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

(30)   and polar bears, which regularly inhabit

treeless environments, rely on aggres-

sion to protect their cubs.  Like brown

      bears and polar bears (and unlike other

myrmecophagous mammals, which are

(35) 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.

(40)  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

(45)   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

(50)   also coexist with and have been killed

by tree-climbing leopards, and are often

confronted and chased by rhinoceroses

and elephants, which can topple trees.

Collectively these factors probably

(55)   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,

(60)   they may have adopted the extra pre-

caution of carrying their cubs.  Although

cub-carrying may also be adoptive for

myrmecophagous foraging, the behavior

of sloth bear cubs, which climb on their

(65)   mother’s back at the first sign of danger,

suggests that predation was a key

stimulus.

Q12:

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

They tend to become aggressive when provoked.

They live almost exclusively in treeless environments.

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

They are inefficient in their locomotion.

They have relatively large canine teeth.

这题以前没有人问。答案是A，定位点我在原文中标出来了。

我要问的是：B为什么不对？B的定位点，我也在原文中标出来了。

请NN们指点！

wangyu73cn

最好不要开新贴，而且标题也不便于检索啊。：）

B:They live almost exclusively in treeless environments.比较绝对了。而且，文中有：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.这里的两个副词不是同一个意思。