尺寸精度IT10—IT13用的范围有( )。 A．农业机械重要部分 B．蒸汽机次_爱下问搜题

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问题单项选择题

尺寸精度IT10—IT13用的范围有( )。

A．农业机械重要部分
B．蒸汽机次要部分
C．农业机器不重要部分
D．重型机床次要部分

答案

参考答案：C

解析：尺寸公差已经标准化，按国家标准，把尺寸公差分为20级。即：IT01、 IT0、IT１～IT18，汀表示标准公差。数字越大，精度越低，加工误差越大，加工越容易，制造成本越低。其中IT10～IT13范围内适用机车车辆、农业机械的不重要部分。

计算题

主族元素R的最高价氧化物0.112g，溶于水制得100g碱性溶液，其浓度为0.148%，R原子核内含有20个中子。通过计算，推测R是什么元素？（要求写出过程。）

完形填空

Failing doesn’t make a failure. True failures are those who don’t learn from their    1  .
Smart persons not only learn from their own mistakes—they pay 2 to the mistakes of others, equate error with opportunity, and learn valuable 3 as well, as this story illustrates (说明).
A lion, a fox, and a wild pig went   4  for rabbits together. By the end of the day, they had a large pile of rabbits to   5 .
The lion said to the wild pig, “Pig, you divide the rabbits up among the three of us in a   6  that you think is fair.” The pig divided the rabbits up into three   7   piles, and said to the lion, “There we are. One   8 for each of us. How’s that?” The lion   9  sprang at the wild pig and 10 him.
Then, the lion threw all the rabbits into one big pile again.
He 11 to the fox. “Well now, Mr. Fox, why don’t you 12 the rabbits between the two of us in a way that you think is fair?”
The fox walked over to the pile of rabbits, took the 13 one for himself, and left the rest in a big pile. “This rabbit is for me, Mr. Lion, and that big pile is for you.” said the fox.
At that point, the lion laughed, “Where did you learn to divide so 14 , Mr. Fox?” And Mr. Fox replied, “The wild pig 15 me.”

D．experiences

C．immediately

小题13:A largest B. narrowest C. smallest D. worst