您要查找的是不是：
- A级管道the A-level pipeline
- 核级管道Nuclear piping
- 100级管道式过滤结构洁净通道的研制Class 100 clean tunnel with filter tube structure
- 摘要核级管道系统的设计是个复杂的优化问题。It is complex optimum problem to design the nuclear piping system.
- 管道pipeline
- 绿A级A-grade green
- 不仅A而且not merely A but also B
- A级表面Class A surface
- A股A-share
- 级联connection
- 管道系统ductwork
- 校级field rank
- 把A误以为take A for B
- 大学英语四级College English Band 4
- 船级ship' classification
- 三级片third-grade film
- 无级stepless
- 级配graduation
- 第二级secondary
- 大学英语六级考试CET-6 [College English Test, Band Six]
