graded tube

例句：

1. 1. The students were given different levels of difficulty in the test.
   学生们在测试中被给予了不同难度级别的题目。
2. 2.The company has a system for grading its employees based on their performance.
   该公司有一个系统，根据员工的表现来评定他们的等级。
3. 3. The graded areas are clearly marked on the map.
   地图上清晰地标出了分级区域。