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Geologists believe that oil and coal are composed of organic molecules______(因为它们本身来自于生物).

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Birdsong A male zebra finch chirps away to himself. Suddenly he notices a female bird nearby. He realizes he has an audience and immediately changes his song. Can the female tell the difference in his performance According to a new study, the female zebra finch knows. And she prefers the special trills he creates when he sings to her. A male zebra finch changes his song when singing to a female in ways that people can barely detect. But the female finch can tell the difference. Scientists had noticed slight variations in the songs of male zebra finches based on whether they were singing alone or whether there was a female (and potential mate) nearby. With an audience, the males sped up the pace of their songs and controlled the notes they used. For this study, researchers Sarah C. Woolley and Allison Doupe at the University of California, San Francisco decided to focus attention on the listening females, which have not been well studied in the past. In the study, Woolley and Doupe set up, a long cage with a sound speaker at each end. One broadcast the sound of a male zebra finch singing to himself, like someone singing in the shower. The other speaker broadcast a male performing for a female audience, as if he was giving a concert. Female birds were placed between the two speakers. Some of the birds had mates, others didn’t. The females shifted around a bit, and then most of them hopped over to sit beside just one speaker. All the birds that made a clear choice liked songs meant for a female audience, even if they’d never met the male. Mated females also had a chance to listen to two different performance songs, one from an unknown male, and one from their mate. They spent more time listening to the concert version of their mates’ songs. This suggests that after a while, females learn to recognize and prefer the songs of their mates. Scientists then studied the brains of the females. They found certain areas of the brain perked up when the birds listened to the concert songs. These brain areas may be involved in recognizing and evaluating the songs, and storing the memories of them. This research deals with what’s called directed communication, when the communicator, or sender, focuses the message for a specific audience. One example is the way moms speak to their babies. Mothers around the world use the same sort of high-pitched sing-song chatter, and the babies respond best to those sounds. Songbirds are one of the only other species known to learn their communication, in this case their songs. What did the researchers find in their study of female zebra finches

A. Female finches liked songs male finches sang for them.
B. Female finches only liked songs male finches sang for their mates.
C. Female finches liked to listen to songs from both speakers.
D. Female finches chose the best male singers as their mates.

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简述合同约定不明时的履行规则。

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增值税纳税人兼营营业税应税劳务未分别核算的，其应税劳务应一并征收增值税。( )

A. 对
B. 错

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Doubts and Debates over the Worth of MBA Bill Gates, the billionaire Microsoft chairman without a single earned university degree, is by his success raising new doubts about the worth of the business world’s favorite academic title: the MBA ( Master of Business Administration). The MBA, a 20th-century product always has borne the mark of lowly commerce and greed (贪婪) on the tree-lined campuses ruled by purer disciplines such as philosophy and literature. But even with the recession apparently cutting into the hiring of business school graduates, about 79,000 people are expected to receive MBAs in 1993. This is nearly 16 times the number of business graduates in 1960, a testimony to the widespread assumption that the MBA is vital for young men and women who want to run companies some day. "If you are going into the corporate world it is still a disadvantage not to have one," said Donald Morrison, professor of marketing and management science. "But in the last five years or so, when someone says, ’ Should I attempt to get an MBA,’ the answer a lot more is: It depends. " The success of Bill Gates and other non-MBAs, such as the late Sam Walton of Wal-Mart Stores Inc. has helped inspire self-conscious debates on business school campuses over the worth of a business degree and whether management skills can be taught. The Harvard Business Review printed a lively, fictional exchange of letters to dramatize complaints about business degree holders. The article called MBA hires "extremely disappointing" and said "MBAs wants to move up too fast, they don’t understand politics and people, and they aren’t able to function as part of a team until their third year. But by then, they’re out looking for other jobs. " The problem, most participants in the debate acknowledge, is that the MBA has acquired an aura (光环) of future riches and power for beyond its actual importance and usefulness. Enrollment in business schools exploded in the 1970s and 1980s and created the assumption that no one who pursued a business career could do with out one. The growth was fueled by a backlash (反冲) against the anti-business values of the 1960s and by the women’s movement. Business people who have hired or worked with MBAs say those with the degrees often know how to analyze systems but are not so skillful at motivating people. "They don’t get a lot of grounding in the people side of the business," said James Shaffer, vice president and principal of the Towers Perrin management consulting firm. What is the major weakness of MBA holders according to The Harvard Business Review

A. They are not good at dealing with people.
B. They keep complaining about their jobs.
C. They are usually self centered.
D. They are aggressive and greedy.

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