级数

例句：

1. 1. The teacher explained the concept of arithmetic in a sequence of steps.
   老师以一系列步骤解释了算术的概念。
2. 2. The team worked in a series of meetings to finalize their plans.
   团队通过一系列会议来最终确定他们的计划。
3. 3. The data was presented in a series of charts and graphs.
   数据被呈现在一系列图表和图形中。