问题
选择题
The old man became very worried, standing at the gate, unable to find a man________he could turn for
help. [ ]
A. from whom
B. at whom
C. into whom
D. to whom
答案
答案：D
搜题请搜索小程序“爱下问搜题”
The old man became very worried, standing at the gate, unable to find a man________he could turn for
help. [ ]
A. from whom
B. at whom
C. into whom
D. to whom
答案：D
某样品为铜和氧化铜的混合物，为测定该样品中氧化铜的含量，取20g此样品，分四次向其中加入稀盐酸与之充分反应．每次所用的盐酸的质量与反应后剩余固体的质量见下表：
| 第次 | 加入稀盐酸的体积/ml | 剩余固体的质量/g |
| 1 | 40 | 16 |
| 2 | 40 | 12 |
| 3 | 40 | 8 |
| 4 | 40 | 8 |
（2）样品中氧化铜的质量分数为______．
（3）稀盐酸溶质质量分数．（计算结果保留两位小数）______．