书面表达。

     你一定有过许多难忘的假期。请你写一篇60个词左右的短文，描述一下你印象最深刻的那个假期。

     要点提示：

     1. Where did you go?

     2. What did you do?

     3. How was the weather there?

     4. How were the people and the food there?

     5. What do you think of it?

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何谓药物的排泄速度?如何从尿药浓度计算排泄速度?写出排泄速度和清除率的关系公式。