问题
选择题
_____ many times, but he still couldn't understand it. [ ]
A. Though he had been told
B. Having been told
C. Having told
D. He had been told
答案
答案：D
搜题请搜索小程序“爱下问搜题”
_____ many times, but he still couldn't understand it. [ ]
A. Though he had been told
B. Having been told
C. Having told
D. He had been told
答案：D
某化学小组的同学爬山时带一些石灰石样品，他们想探究其中碳酸钙的质量分数．于是取4g样品放入烧杯中（杂质不溶于水，也不与酸反应），然后取40g稀盐酸平均分四次加入，反应情况如下表：
| 稀盐酸质量/g | 10 | 10 | 10 | 10 |
| 剩余固体质量/g | 3g | 2g | 1g | 1g |
（2）所用稀盐酸中溶质的质量分数？