问题
选择题
It_____ him one hour______ the exercises yesterday.[ ]
A. takes; to do
B. took; to do
C. takes; doing
D. took; doing
答案
答案：B
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It_____ him one hour______ the exercises yesterday.[ ]
A. takes; to do
B. took; to do
C. takes; doing
D. took; doing
答案：B
下表列出了除去物质中所含少量杂质的方法，其中不正确的是 （ ）
| 选项 | 物质 | 所含杂质 | 除去杂质的方法 |
| A | CO2 | CO | 将气体缓缓通过灼热的氧化铜 |
| B | CuO | C | 隔绝氧气灼烧 |
| C | Cu | Zn | 加入过量的稀盐酸，过滤，洗涤，干燥 |
| D | CaO | CaCO3 | 高温煅烧 |