下列对胡萝卜素提取过程的分析正确的是（　　）

实验室常利用甲醛法测定(NH₄)₂SO₄样品中氮的质量分数，其反应原理为：4NH＋6HCHO===3H^＋＋6H₂O＋(CH₂)₆N₄H^＋滴定时，1 mol(CH₂)₆N₄H^＋与1 mol H^＋相当，然后用NaOH标准溶液滴定反应生成的酸，某兴趣小组用甲醛法进行了如下实验：

步骤 Ⅰ　称取样品1.500 g。

步骤 Ⅱ　将样品溶解后，完全转移到250 mL容量瓶中，定容，充分摇匀。

步骤 Ⅲ　移取25.00 mL样品溶液于250 mL锥形瓶中，加入10 mL 20%的中性甲醛溶液，摇匀、静置5 min后，加入1～2滴酚酞试液，用NaOH标准溶液滴定至终点。按上述操作方法再重复2次。

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    At a sports meet of high school I knew Christie and we became best friend. At that time, we often spend time together. Under her help, I made great progress in my study. Last year, she decided to study in abroad. In other words, we would be separated for long time. Before she leaving , I prepared a gift to show my best wishes to him. She said it was the best gift she has ever had. Until then, we've kept in touch with each other through e-mails. I look forward to see her again in the near future.