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| 1. | It became necessary to provide drainage or sewer systems to carry such wastes away from the area. |
| 提供排水系统或污水管道系统，把废物排出市区已成为必要。 |
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| 2. | It may also provide drainage and give added protection against frost action when necessary. |
| 它具有排水作用，但在需要时也增加保护抗冻作用。 |
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| 3. | The crushed rock is called ballast, and it severs both to distribute the load and to provide drainage |
| 在传统的铁路施工中，基础平整完毕以后再铺上碎石子。这种碎石子叫做道碴，用来分散负荷和排水。 |
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| 4. | If a large enough bile duct can be found to anastomose and provide bile drainage, then surgery can be |
| 如果有足够大的胆管可进行吻合并提供胆汁引流，该病即能够通过手术治愈。 |
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