一组变量值，其大小分别为13，10，12，9，8，11，98。问算术均数是（）
A.23
B.11
C.12
D.10
E.10.5
参考答案：A
句型转换。
1. We can wear hats in school. (变成否定句)
_____________________________
2. We can eat in the cafeteria. We can't eat in the classroom. (用but 将两句话连接起来)
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3. You have to wear sneakers for gym class. (变成一般疑问句,并作肯定回答)
4. I have to do my homework after school. (就划线部分提问)
5. I have to be in bed by ten o'clock. (就划线部分提问)
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but 将两句话连接起来)