两级
He was my senior at Yale by two years. 他是耶鲁大学比我高两级的学生。
The project took place during the teacher's in-school probationary teaching period, and had two stages. 研究共分二阶段进行。
In some cases, a two-stage severe hydrotreater using Ni-Mo and precious metal catalysts in the first and the second stage respectively can be used. 有时更得采用二阶段制程，前后段分别使用镍钼和贵金属触媒。
