通常用复数，复数是levels，例如：

1. Wage rates depend on levels of productivity.工资水平取决于生产量的多寡。

2.They were required to cut pollution levels, on pain of a £ 10 000 fine if they disobeyed.他们被要求降低污染水平，违则罚款1万英镑。

3. It is important not to let production levels fall.重要的是别让产量滑落。