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| clean air | |||
| scavenging air | |||
| 清洁空气: 33 phrases in 14 subjects |
| Automobiles | 5 |
| Aviation | 3 |
| Business | 1 |
| Chemistry | 1 |
| Ecology | 3 |
| Electronics | 2 |
| Environment | 4 |
| Household appliances | 1 |
| Management | 1 |
| Oil / petroleum | 1 |
| Oil processing plants | 2 |
| Refrigeration | 2 |
| Shipbuilding | 3 |
| Technology | 4 |