问题
单项选择题
X射线荧光光谱仪采用（）作为分光元件。
A、棱镜
B、光栅
C、晶体
D、入射狭缝
答案
参考答案：C
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X射线荧光光谱仪采用（）作为分光元件。
A、棱镜
B、光栅
C、晶体
D、入射狭缝
参考答案：C
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| Last weekend, my kids along with a few other kids from the neighborhood volunteered to help me wash my car. My 10-year-old daughter came up with the idea of 1 other people's cars as well. It was pretty 2 outside and I had no plans to 3 being in the bright sun. she 4 wanted to give lemonade(柠檬汽水) to passers-by for free. I had seen little kids 5 and sell fresh lemonade for a small cost but not free. Although I felt confused, I decided to help her. Then she asked me, "What if we 6 this a smile car wash?" I couldn't hold back my tears and 7 her and the other kids to go outside the house and come up with 8 ideas. While I kept myself busy in drying the car, the kids walked up to me with a(n) 9 with beautiful images of smiles. They had "Free Car Wash" written on it and the 10 of their exercise was "smile". It was pretty neat to see a team of kids ranging 5-11 years with the duty to do something for others. All that seemed 11 and came right from their heart. Nothing seemed to 12 to them: their playtime, the heat outside--- they just wanted to help others and do something nice in the community! I helped them make some fresh lemonade and brought out some additional cloth to help clean cars. Passers-by were 13 and one even shouted back to them saying, "God Bless You, my kids… | ||||
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