问题
单项选择题
以下说法正确的是（）
A.库塔-茹可夫斯基定理对流体具有普适性。
B.如果流动存在势函数，则也存在流函数。
C.涡量输运方程表明破坏旋涡守恒的根源是粘性作用。
D.流层之间的内摩擦力与接触面上的压力无关。
答案
参考答案：D
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以下说法正确的是（）
A.库塔-茹可夫斯基定理对流体具有普适性。
B.如果流动存在势函数，则也存在流函数。
C.涡量输运方程表明破坏旋涡守恒的根源是粘性作用。
D.流层之间的内摩擦力与接触面上的压力无关。
参考答案：D
| 完形填空。 | |||
| A professor(教授) told his students to go into the city slums (贫民窟) to study the life of 200 boys. He asked them to 1 reports about each boy’s life and future. Every one of the students wrote, “He doesn’t have any hope.”Twenty-five years 2 , another professor read about the earlier study. He told his students to ___3___ what had happened to the boys. They tried very had and found that 176 of the boys had became successful 4 doctors, teachers and scientists.The professor was very 5 and decided to study it further. Luckily, all the men were living near the place and he was able to ask each one, “What made you 6 ?” Each one answered, “There was a teacher.”The teacher was 7 living there, so the professor found her and asked the old woman 8 she had used to pull those boys 9 the slum, and change them into successful people.The teacher’s 10 began to shine and said with a sweet smile, “It’s really very easy. I love those boys.” | |||
( )1. A. read | B. study | C. write | D. take |