题干

先秦著作《山海经·海内经》记载:“后稷(后稷是古代周族始祖)播百谷。稷之孙曰叔均,始作牛耕。”从考古发现来看,在河南、山西、江苏、浙江、上海、广西、内蒙古、吉林等省市出土了商周时期的石犁。这说明(    )

A:历史记述的正误需要考古发现佐证

B:文献资料不能作为一手史料

C:商周时期我国就出现了铁犁牛耕

D:我国使用牛耕技术的历史久远

上一题 下一题 0.0难度 选择题 更新时间:2019-06-17 05:22:12

答案(点此获取答案解析)

D

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    A 15-year-old student who invented a flashlight(手电筒) getting power from the holder's body heat is going home today from California with a big prize and a chance to do further research.

    Ann Makosinski was the only Canadian among the four winners at Google's international science competition. Thousands of young scientists from around the world took part in the competition.

    Winning the science and technology competition was "a surprise". Ann said, "I think it will have a great influence on my future."

    Ann thanked her family for encouraging her interest in science and said that her first toy was a box of transistors(晶体管).

    Ann's prize includes $ 25,000 and a "once in a-lifetime expericnce" from Google for her Hollow Flashlight, which has no moving parts or batteries.

    The idea for the invention came from seeing unwanted batteries and her friend's experience. When Ann visited a friend in the Philippines, she saw the friend couldn't study when it became dark because there was no electricity or light. She saw the need for a flashlight that has no batteries - Hollow Flashlight.

    In her project, Ann wrote "I made two flashlights that do not use any batteries or harmful materials. They do not create any noise and will always work. The flashlight needs at least a 5℃ temperature difference between the holder's body and the environment around to produce light."

    A video of Ann explaining how she creatcd the flashlight has been watched more than 1.4 million times on the Internet.

    Though Ann was successful, she has not made a decision about her career path. Ann hopes that she can find a way to join her love of film and science together.

    The four winners were chosen from 15 final competitors from eight countries. The competition attracted thousands of students in 120 countries.