每个行业都要经历一个由成长到衰退的发展演变过程，这个过程便称为行业的生命周期。一般地，行业的生命周期可分为幼稚期、成长期、成熟期和衰退期。( )
参考答案：对
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)
干燥综合征的标志抗体（）
A.抗ds-DNA抗体
B.抗RNP抗体
C.抗CCP抗体
D.抗SSA和SSB抗体
E.抗Jo-1抗体
but 将两句话连接起来)