问题
选择题
The biggest room in this building _____ used as a meeting room. [ ]
A. used to
B. is used to
C. used to be
D. is used to be
答案
答案：C
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The biggest room in this building _____ used as a meeting room. [ ]
A. used to
B. is used to
C. used to be
D. is used to be
答案：C
下表是某反应在T1和T2时刻（T2＞T1）测得的有关数据：
| 物质 | A | B | C | D |
| T1时刻质量/g | 2 | 4.8 | 19.75 | 7.45 |
| T2时刻质量/g | 2 | 9.6 | 7.5 | X |
（2）写出一例与上述反应类型相同的化学方程式：______
（3）根据相对原子质量与各物质质量的变化关系，写出相应的化学方程式：______．