问题
选择题
—When is Ann's birthday?
—_______ birthday is September 5th.[ ]
A. His
B. My
C. Its
D. Her
答案
答案：D
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—When is Ann's birthday?
—_______ birthday is September 5th.[ ]
A. His
B. My
C. Its
D. Her
答案：D
今年全国人大和政协会议使用了一种含碳酸钙的“石头纸”．为测定其中碳酸钙的含量，课外活动小组的同学称取50g碎纸样品．分别在5只烧杯中进行了实验，实验数据见下表（假设纸张其它成分既不溶于水，也不与水反应）：
| 烧杯① | 烧杯② | 烧杯③ | 烧杯④ | 烧杯⑤ | |
| 加入样品的质量/g | 10 | 10 | 10 | 10 | 10 |
| 加入稀盐酸的质量/g | 10 | 20 | 30 | 40 | 50 |
| 生成气体的质量/g | 0.88 | 1.76 | 2.64 | 3.52 | 3.52 |
（2）实验中所用稀盐酸的溶质质量分数．