问题
单项选择题
机床精度检验时，由丝杠所产生的螺距累积误差，当Da≤2000时在任意300mm测量长度内允差值为（）mm。
A、0.02
B、0.03
C、0.04
D、0.05
答案
参考答案：C
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机床精度检验时，由丝杠所产生的螺距累积误差，当Da≤2000时在任意300mm测量长度内允差值为（）mm。
A、0.02
B、0.03
C、0.04
D、0.05
参考答案：C
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| William Franklin came to my class half a year ago. But from his first day here, he 1 himself in his own world and he never spoke to others. As his teacher, I tried to start a talk with him but 2 . It seemed as if he just didn't want to break his 3 . After the Thanksgiving holiday, we received the news of the 4 Christmas collection of money for the 5 in our school."Christmas is a season of 6 , " I told my students."Some poor students in our school might not have a 7 holiday. By giving a little money, you will help 8 some toys, food and clothing for these needy students. We will 9 the collection tomorrow." The next morning, 10 , I found out almost everyone had 11 this matter except Willard Franklin. He came up to my desk with his head down. 12 , he dropped two coins into the small box."I don't need milk for lunch," he said in a 13 voice. After school I couldn't help sharing what had 14 in the morning with our headmaster. "I may be wrong, but I 15 Willard might be ready to become part of our class."" I am 16 to hear that," he nodded. "And I just received a list of the poor families in our school who most need 17 . Here, take a look at it." As I sat down to 18 , I found Willard Franklin was at the top of the list. At that moment, I felt I really 19 Willard for the first time: a cold face with a warm heart. From this 20 , I also learnt that whether rich or poor, every child has a kind heart. | ||||
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