D.Teachers are able to find jobs that are less demanding yet more rewarding.

[答案]B

25.Which of the following******in meaning to.

the underlined phrase"take a toll on"in the 1a*****.

A.Be in charge of

B.Be dependent on

C.Have an effect on

D.Take advantage of

[答案]C

阅读理解，回答26-30题

Passage 2

As a species,*****incredibly smart.We tell stories,create magnificent art and astounding technology,build cities,and explore space.We haven't been around nearly as long as many other species,but in many respects we've accomplished more than any*.We eat them and they don't eat us.We even run scientific***on them--and are thinking about re-creating

****those that have gone extinct.But our intelligence comes with a curious caveat:our babies are among the dumbest-or,rather,the most helpless--that exist.A baby******an stand within an hour of birth,and can even*****flee predators on its frst day of life.A baby monkey can grasp its mother and hang on for protection and nourishment.****infant

can't even hold up its own head.

The evolution of***intelligence isn't something that Celeste Kidd had ever pondered.A developmental cognitive scientist who currently works at the University of Rochester,her work had focussed mostly on learning and decision-making in children.Over years of***oung children,she became impressed with the average child's level of sophistication.But when she looked at the****sh encountered,she saw a baffling****of

helplessness:How****they be so incompetent one second and so so soon*****One day,she posed the question to her colleague Steven Piantadosi.

"Both of us wondered what could possibly justify the degree of helplessness human infants**she told me****."Even other primate babies,like baby chimps,which are close in evolutionary terms,can cling onto their moms."She began to see a contradiction:***are born quite helpless,far more so than any other primate,but,fairly early on,we start becoming quite smart,again far more so than any other primate.What if this weren't***so much as a causal pathway?

That's the argument that Kidd and***make in their new paper,published in a June issue of PNAS.Humans become so intelligent because***infants

are so incredibly helpless,they argue;the one necessitates the other.

The theory is startling,but it isn't entirely new.***have been pondering the peculiarities of our birth and its evolutionary significance for***some***.Humans***to the subset of mammals,****viviparous mammals,that give live birth to their young.This***that infants must grow to a mature enough state inside the body to be born,but they can't be so big that they are unable to come out.This leads to a trade-of:the more**

****an animal is,the larger its head generally is,but the birth canal imposes an upper limit o1n just how large that head can***it gets stuck.The brain,therefore,must keep maturing,and th*****continue growing,long after birth.***intelligent an animal will eventually be,the mor*****immature its brain is at birth.

Researchers have long known*****trade-off,*****the connection between brain size and neural density and intelligence.For instance,Robin****found that the ratio of neocortical volume to brain size can predict the social-group size in a****of species,****bats,cetaceans,and primates,

while Simon Reader has demonstrated links in tool use and innovation to brain size in primates.Kidd and*****new idea is that increased helplessness******mandates increased****in parents--and that a runaway

selection dynamic can account for both.Natural selection favors humans with******because those humans tend to be smarter.This may create evolutionary incentives for babies****born at an even earlier developmental stage,****require more intelligence to***.*This creates the dynamic:over time,helpless babies make parents more****.which makes babies more helpless,which makes the*****intelligent,and so on.

26.According to paragraph 1,***of the following is true?

A.Some species are smarter than human beings.

B.Extinct species have been re-created by scientists.

C.Babies of other species are smarter than human infants.

D.Fewer species are earlier inhabitants than human beings.

[答案]C

27.What surprised****Kidd regarding children's***maturation?

A.Infants'helplessness when they are born.

B.Children'S high intelligence when they grow up.

C.Children'S leap from helplessness to sophistication.

D.Children'S incompetence in learning and decision-making.

[答案]C

28.What can we***form Paragraph 3***brain development?

A.Babies'helplessness at birth is an indication of human intelligence

B.Other mammal brains are more mature than human brain at birth.

C.Only itelligent mammals give live birth to their babies.