问题
单项选择题
根据产生误差的原因来分，误差可分为（）。
A、偶然误差和系统误差
B、偶然误差和方法误差
C、系统误差和试剂误差
答案
参考答案：A
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根据产生误差的原因来分，误差可分为（）。
A、偶然误差和系统误差
B、偶然误差和方法误差
C、系统误差和试剂误差
参考答案：A
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| When Mary Smith was a student, she wanted to be a 1___________ 2___________ she liked children. When she was twenty 3___________, she taught (教学) in a small school. She was a good teacher, and she 4___________ a lot with her children in her class. They loved her very much. One day, a girl in her class 5___________ to her, " Miss Smith, why does a man's hair become grey (灰白色) before his beard (胡子) does? " Mary laughed and said, " I don't know. Helen, do you know? " " Sorry, but it happened 6___________ my father." The other 7___________ laughed when they heard this. Then a boy said, " I 8___________, Miss Smith! A man's hair becomes grey 9___________ because it's sixteen years older 10___________ his beard! "
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