问题
单项选择题
气阀阀面与阀座为外接触式配合，即阀面锥角小于座面锥角，通常小（）。
A．0.5°～1°
B．1°～1.5°
C．1.5°～2°
D．2°～2.5°
答案
参考答案：A
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气阀阀面与阀座为外接触式配合，即阀面锥角小于座面锥角，通常小（）。
A．0.5°～1°
B．1°～1.5°
C．1.5°～2°
D．2°～2.5°
参考答案：A
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| School students in China have been learning dance for a year since 2008. Are they doing well? On September, 2008, a dance competition was 1 in Xi'an. Let's take a look. More than 2,500 students from 40 schools 2 the competition. The Middle School affiliated (附属的) to Xi'an Jiaotong University was the 3 of all the junior teams. The 100 students of the school were happy to 4 the first prize. They made their dance special 5 a "five Olympic rings" pattern (形状). They also 6 the waltz and the traditional yangge dance. No pains, no gains. The students said they had been practising for 7 half a year. "We were nervous at first 8 we didn't know each other," said Zeng Jingyi, a 13-year-old girl. "What's more, the boys were clumsy (笨拙的) and often stepped on the girls' 9 !" Only practice makes perfect. The students practiced more than three hours a day."Sometimes I saw boys playing basketball in the playground," said Xu Rui, a 13-year-old boy. "How I wanted to join them! But I didn't. Dancing can be 10 too. We should work hard for our school's honor." | ||||
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