问题
单项选择题
The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions.
A.sometimes
B.all times
C.never
D.partly
答案
参考答案：C
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The quality of EGC messages is（）affected by the position of the ship, the time of reception and climatic conditions.
A.sometimes
B.all times
C.never
D.partly
参考答案：C
有机物在反应中，常有原子间的共价键全部或部分断裂，如C—H、C—C、C=C、C—O、C=O等。下列各反应中，反应物分子中断裂键的排列，正确的组合是
| 化学反应 | 乙醇酯化 | 乙醇与钠 | 乙醛氧化 | 乙醛加氢 |
| A | O—H | C—H | C—H | C—O |
| B | O—H | O—H | C—H | C=O |
| C | C—O | C—O | C—H | C=O |
| D | C—O | C—H | C—C | C—O |