题目内容：

Marmoset monkeys exist on a branch of the evolutionary tree that is distinct from the one that led to mans. But they constantly astonish researchers with ________ behavior that seems pretty highly evolved. Their social organization and ________ practices could have been the model for the phrase “It takes a village.” A dominant male and female breed, and their babies are carefully looked after by extended family members who then aren't free to breed themselves.

A new study further ________ the marmoset’s reputation for admirable community values. Researchers report that these caregivers share their food more generously with little ones ________ than when they’re surrounded by the watchful eyes of other community members. In complex societies where individuals band together for ______ protection, researchers have come up with a few widely accepted explanations for selfless behavior. But specific acts, like sharing a delicious cricket(蟋蟀) with a begging baby marmoset, seem to need more ______ explanation

One possibility is that an individual practices ______ as a means of enhancing his status among peers. By ______ that he is so well gifted with material goods that he can give some away, this do-gooder enhances his power within the group. That, in turn, may ______ prospective mates. The other explanation for charitable behavior ______ that kindnesses extended to others are simply the fees of group membership, which offers some future promise of a chance to mate. Failure to share would result in exclusion from the group and a loss of ______ partners. Scientists call this the “pay to stay” model. Importantly, for both of these models to work, acts of kindness must have a(n) ______. That suggests you would see more sharing in group settings; away from judging eyes, a caregiver might be more likely to keep food for himself or herself. And yet, in 2,581 tests conducted with 31 adult and 14 baby marmosets, the ______ appeared to be true

Anthropologists (人类学家) from the University of Zurich carefully documented how often, in groups and in conditions that found caregiver and baby separated from the crowd, an adult would share his or her cricket. When alone with a baby begging for a taste, adult marmosets shared their cricket 85% of the time. When in a group, caregivers offered up their cricket 67% of the time.” Our results show that helping in common marmosets is not driven by reputation management or ______ avoidance, “ the study authors reported Rather, it is driven by a deep-down motivation to help that is more ______ expressed when individuals are alone with young.”

1.A. animal    B. careful    C. social    D. individual

2.A. evolving    B. communicating    C. organizing    D. parenting

3.A. shines    B. damages    C. affects    D. protests

4.A. at play    B. in private    C. on schedule    D. by accident

5.A. adequate    B. effective    C. continual    D. mutual

6.A. creative    B. complex    C. specific    D. official

7.A. generosity    B. wisdom    C. independence    D. governance

8.A. promising    B. demonstrating    C. pretending    D. explaining

9.A. count on    B. go after    C. appeal to    D. benefit from

10.A. assumes    B. confirms    C. enhances    D. concludes

11.A. regular    B. dominant    C. potential    D. previous

12.A. atmosphere    B. audience    C. feedback    D. judge

13.A. statistics    B. expectation    C. argument    D. opposite

14.A. responsibility    B. punishment    C. arrangement    D. difficulty

15.A. strongly    B. causally    C. delicately    D. fearlessly