指出下列情况分别属于系统误差还是随机误差（1）天平使用前未调平衡（）（2）千分尺零点
题型：填空题
问题：
指出下列情况分别属于系统误差还是随机误差
（1）天平使用前未调平衡（）
（2）千分尺零点不（）
（3）游标的分度不均匀（）
题型：填空题
阅读理解。
American schools’ beginning is in September after a long summer holiday. There are two terms in a
school year. The first term is from September to January, and the second is from February to June. Most American children begin to go to school when they are five years old. Most students are seventeen or
eighteen years old when they finish high school.
High school students take only four or five subjects each term. They usually go to the same classes e
very day, and they have homework for every class. After class they do many interesting things.
After high school, many students go to college. They can go to a small one or a large one. They usually
have to give a lot of money. So many college students work after class to get the money for their studies.
1. How many terms are there in a school year in America ?
A. Four
B. One
C. Three
D. Two
2. The first term is ______.
A. from February to June
B. from January to September
C. from June to February
D. from September to January
3. When a child is ______ years old he or she can go to school.
A. five
B. four
C. seven
D. six
4.How many subjects do the high school students take each term ?
A. As many as they like.
B. Five. 
C. Four.
D. Four or five.
5. Why do many college students have to work after class ?
A. Because some work is helpful to their studies.
B. Because the teachers ask them to do so.
C. Because they like to work very much.
D. Because they need to get money for their studies.