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| multiple echo | |||
| 多 次回波: 9 phrases in 8 subjects |
| Acoustics | 1 |
| Air defense | 1 |
| Construction | 1 |
| General | 1 |
| Information technology | 1 |
| Metallurgy | 1 |
| Oil / petroleum | 1 |
| Technology | 2 |
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