题干

石墨烯是现在世界上最薄且最坚硬的纳米材料,其理论厚度仅是 0.00000000034m ,这个用科学记数法表示正确的是(  )

A:3.4×109

B:0.34×109

C:3.4×1010

D:3.4×1011

上一题 下一题 0.0难度 选择题 更新时间:2020-02-17 12:10:38

答案(点此获取答案解析)

C

同类题1

阅读理解

    Sitting on the sofa in her family's Michigan home in 2009, looking through the Guinness World Records, 10 year-old Winter Vinecki was surprised to find that the record for the youngest person to complete a marathon on every continent was held by a 27-year-old man. “I can beat that,” she declared. “For Dad. ” And she had every reason to believe she could.

    A natural athlete since the age of 5, Winter had been running together with her mom and uncle, both athletes, and competing in races across the country. Soon, her name was appearing in national competitions. Trophies (奖牌) lined her walls.

    But in 2008, at the age of 9, Winter stopped racing for medals. In May of that year, her father found out he had caught a rare cancer. To raise awareness and funds to fight the disease. Winter started an organization called I earn Winter. Just 10 months after his diagnosis, her father passed away.

    Over the next three years, Winter came first in 20 of the 37 races in which she competed, including four Junior Olympics Cross Country Championships. Along the way, she raised over $ 400,000 to help find a cure for cancer.

    Now 14, Winter is working on her world record to win her cause a place in the Guinness World Records. She recently completed her first marathon in Eugene, Oregon, a race normally limited to runners over 16, finishing in an amazing 3:45:04. “I'm used to racing with adults, and I think it's kind of fun to race past them,” said Winter before the race.

    With six continents to go, Winter has just begun a journey that will take her two years. “Every time I step to a starting line,” Winter says, “I have one thought in mind: keeping my dad's spirit alive.”