In 1784, five years before he became president of the United States, George Washington, 52, was nearly toothless. So he hired a dentist to transplant nine teeth into his jaw—having extracted them from the mouths of his slaves. That’s a far different image from the cherry-tree-chopping George most people remember from their history books. But recently, many historians have begun to focus on the roles slavery played in the lives of the founding generation. They have been spurred in part by DNA evidence made available in 1998, which almost certainly proved Thomas Jefferson had fathered at least one child with his slave Sally Hemings. And only over the past 30 years have scholars examined history from the bottom up. Works of several historians reveal the moral compromises made by the nation’s early leaders and the fragile nature of the country’s infancy. More significantly, they argue that many of the Founding Fathers knew slavery was wrong—and yet most did little to fight it. More than anything, the historians say, the founders were hampered by the culture of their time. While Washington and Jefferson privately expressed distaste for slavery, they also understood that it was part of the political and economic bedrock of the country they helped to create. For one thing, the South could not afford to part with its slaves. Owning slaves was "like having a large bank account," says Wiencek, author of A n Imperfect God: George Washington, His Slaves, and The Creation of America. The southern states would not have signed the Constitution without protections for the "peculiar institution," including a clause that counted a slave as three fifths of a man for purposes of congressional representation. And the statesmen’s political lives depended on slavery. The three-fifths formula handed Jefferson his narrow victory in the presidential election of 1800 by inflating the votes of the southern states in the Electoral College. Once in office, Jefferson extended slavery with the Louisiana Purchase in 1803; the new land was carved into 13 states, including three slave states. Still, Jefferson freed Hemings’s children—though not Hemings herself or his approximately 150 other slaves. Washington, who had begun to believe that all men were created equal after observing the bravery of the black soldiers during the Revolutionary War, overcame the strong opposition of his relatives to grant his slaves their freedom in his will. Only a decade earlier, such an act would have required legislative approval in Virginia. We may infer from the second paragraph that ______.
A. DNA technology has been widely applied to history research
B. in its early days the U.S. was confronted with delicate situations
C. historians deliberately made up some stories of Jefferson’s life
D. political compromises are easily found throughout the U.S. history
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It’s one of our common beliefs that mice are afraid of cats. Scientists have long known that even if a mouse has never seen a cat before, it is still able to detect chemical signals released from it and run away in fear. This has always been thought to be something that is hard-wired into a mouse s brain. But now Wendy Ingram, a graduate student at the University of California, Berkeley, has challenged this common sense. She has found a way to "cure" mice of their inborn fear of cats by infecting them with a parasite, reported the science journal Nature. The parasite, called Toxoplasma gondii, might sound unfamiliar to you, but the shocking fact is that up to one-third of people around the world are infected by it. This parasite can cause different diseases among humans, especially pregnant women—it is linked to blindness and the death of unborn babies. However, the parasite’s effects on mice are unique. Ingram and her team measured how mice reacted to a cat’s urine (尿) before and after it was infected by the parasite. They noted that normal mice stayed far away from the urine while mice that were infected with the parasite walked freely around the test area. But that’s not all. The parasite was found to be more powerful than originally thought—even after researchers cured the mice of the infection. They no longer reacted with fear to a cat’s smell, which could indicate that the infection has caused a permanent change in mice’s brains. Why does a parasite change a mouse’s brain instead of making it sick like it does to humans The answer lies in evolution. "It’s exciting scary to know how a parasite can manipulate a mouse’s brain this way," Ingram said. But she also finds it inspiring. "Typically if you have a bacterial infection, you go to a doctor and take antibiotics and the infection is cleared and you expect all the symptoms to also go away." She said, but this study has proven that wrong. "This may have huge implications for infectious disease medicine." The passage is mainly about ______.
A. mice’s inborn terror of cats
B. the evolution of Toxoplasma
C. a new study about the effects of a parasite on mice
D. a harmful parasite called Toxoplasma gondii
光票托收广泛用于非贸易结算,或贸易从属费用的收款等。
A. 对
B. 错
In 1784, five years before he became president of the United States, George Washington, 52, was nearly toothless. So he hired a dentist to transplant nine teeth into his jaw—having extracted them from the mouths of his slaves. That’s a far different image from the cherry-tree-chopping George most people remember from their history books. But recently, many historians have begun to focus on the roles slavery played in the lives of the founding generation. They have been spurred in part by DNA evidence made available in 1998, which almost certainly proved Thomas Jefferson had fathered at least one child with his slave Sally Hemings. And only over the past 30 years have scholars examined history from the bottom up. Works of several historians reveal the moral compromises made by the nation’s early leaders and the fragile nature of the country’s infancy. More significantly, they argue that many of the Founding Fathers knew slavery was wrong—and yet most did little to fight it. More than anything, the historians say, the founders were hampered by the culture of their time. While Washington and Jefferson privately expressed distaste for slavery, they also understood that it was part of the political and economic bedrock of the country they helped to create. For one thing, the South could not afford to part with its slaves. Owning slaves was "like having a large bank account," says Wiencek, author of A n Imperfect God: George Washington, His Slaves, and The Creation of America. The southern states would not have signed the Constitution without protections for the "peculiar institution," including a clause that counted a slave as three fifths of a man for purposes of congressional representation. And the statesmen’s political lives depended on slavery. The three-fifths formula handed Jefferson his narrow victory in the presidential election of 1800 by inflating the votes of the southern states in the Electoral College. Once in office, Jefferson extended slavery with the Louisiana Purchase in 1803; the new land was carved into 13 states, including three slave states. Still, Jefferson freed Hemings’s children—though not Hemings herself or his approximately 150 other slaves. Washington, who had begun to believe that all men were created equal after observing the bravery of the black soldiers during the Revolutionary War, overcame the strong opposition of his relatives to grant his slaves their freedom in his will. Only a decade earlier, such an act would have required legislative approval in Virginia. George Washington’s dental surgery is mentioned to ______.
A. show the primitive medical practice in the past
B. demonstrate the cruelty of slavery in his days
C. stress the role of slaves in the U.S. history
D. reveal some unknown aspect of his life
Psychology tells us that many people hate to take risks. But it is good for us to take risks, especially when the risk is to achieve a desired result. In that way, we become stronger and braver. Our human nature should be to take risks, but some people just sit and wish they didn’t have the fear to move on. This is because they failed a few times in their lives. Please step out and don’t let the past hold you back from living life to the fullest. Move forward and move on! In studying the psychology of taking risks, we find that human provides us with the desire to experiment and take chances. Risk taking is a great advantage that allowed our ancestors to become stronger and stronger day by day. By taking risks they fought off enemies and discovered new territories. This attitude has become a part of our modern culture. Riding a roller caster is a common risk taking activity. Even each person seems to enjoy the risk although they have the understanding that it is dangerous. This psychological and biological connection creates an interesting connection between what is unsafe and what humans enjoy. Getting in a car each day is a risk. Getting out of bed is a risk, too. We need to take risks so that we can complete many things. Astronauts take risks when they get inside a rocket; however, the things they achieve are great. Businessmen take a risk when they buy parts of a company, however, without doing that, they could not make more money. We need to take risks so that we can gain something. It is impossible to move forward in life, earn money, enjoy a relationship, play a sport, or doing anything else without taking a risk. It is all part of the game. It’s one of the most important parts of life. Some people don’t want to take risks, mainly because ______.
A. they are too lazy to move on
B. they feel pleased with the present life
C. they have failed several times before
D. they show little interest in the strange world outside