问题
单项选择题
气压的静力学定义表明，某地的气压等于（）。
A.其下单位体积空气微团的重量
B.其上单位体积空气微团的重量
C.其下单位截面气柱的重量
D.其上单位截面气柱的重量
答案
参考答案：D
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气压的静力学定义表明，某地的气压等于（）。
A.其下单位体积空气微团的重量
B.其上单位体积空气微团的重量
C.其下单位截面气柱的重量
D.其上单位截面气柱的重量
参考答案：D
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| I work as a volunteer (志愿者) for an organization that helps the poor in Haiti. Recently I took my son Barrett there for a week, hoping to 1 him. Before setting out, I told Barrett this trip would be tiring and 2 . For the first two days, he said almost nothing. I worried the trip was too 3 for a 17-year-old. Then on day three, as we were 4 over high rocky mountains, he turned to me and grinned (咧嘴笑), "Pretty hard." After that there was no turning back. A five-year-old girl, wearing a dress several sizes 5 large and broken shoes, followed Barrett around, mesmerized (着迷). He couldn't stop 6 . Later he said 7 . "I wish I could speak French." I was 8 －this from a boy who hated and 9 French classes throughout school. Usually silent, he 10 Gaby, our host, and kept asking questions about the country and its people. He blossomed (活泼起来). 11 , the moment that really took 12 breath away occurred in a village deep in the mountains. I was 13 a woman villager for an article. 135 centimeters tall, she was small in figure but strong in 14 . Through determination, she had learned to read and write and 15 to become part of the leadership of the 16 . Learning her story, Barrett was as 17 as I by this tiny woman's achievements. His eyes were wet and there was a 18 of love and respect on his face. He had finally understood the importance of my work. When leaving for home, Barrett even offered to stay 19 as a volunteer. My insides suddenly felt struck. This 20 achieved all I'd expected. Soon he will celebrate his 18th birthday. He'll be a man. | ||||
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