阶梯倍投法简介：Li Yun knocked on the table with her pen and said dissatisfied: You two, don't talk in class, especially you, Liu Lei, you are disturbing me with your ideas for the composition.
Li Yun knocked on the table with her pen and said dissatisfied: You two, don't talk in class, especially you, Liu Lei, you are disturbing me with your ideas for the composition.
