题干

如图所示,P、Q是两种透明材料制成的两块直角梯形的棱镜,叠合在一起组成一个长方体。某单色光沿与P的上表面成θ角的方向斜射向P,其折射光线正好垂直通过两棱镜的界面。已知材料的折射率nP<nQ,则下列说法正确的是

A:一定没有光线从Q的下表面射出

B:从Q的下表面射出的光线一定与入射到P的上表面的光线平行

C:如果光线从Q的下表面射出,出射光线与下表面所夹的锐角一定大于θ

D:如果光线从Q的下表面射出,出射光线与下表面所夹的锐角一定小于θ

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D

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    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.”