A compressor should never be stopped （）.
A. without first cooling it
B. without first heating it
C. without first unloading it
D. without first loading it
一个产品的生命周期包含的环节是（）
A. 原材料加工
B. 产品制造
C. 产品使用
D. 循环利用
If you had taken the medicine yesterday, you（）much better now.
A. must have felt
B. might have felt
C. would have felt
D. would feel
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