产品生命周期是指某一个工业产品( )所经历的时间。
A. 从投入研制开始到企业破产为止
B. 从投入研制开始到退出市场为止
C. 从完成研制、投入市场开始到退出市场为止
D. 从完成研制、投入市场开始到企业破产为止
--I wish I had succeeded in competitions. -- Yeah, I know. But ______ hard
A. did you work
B. do you work
C. had you worked
D. have you worked
牛带绦虫
A. 成虫
B. 幼虫
C. 两者均可
D. 两者均不可
--How about some coffee -- It's very kind of you.
A. That's all right
B. It tastes nice and sweet
C. Just a little, please
D. I enjoyed it very much
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