stack desulfurization

例句：

1. 1. The boxes are stacked neatly on the shelves.
   盒子整齐地堆放在架子上。
2. 2. The workers were stacking crates in the warehouse.
   工人们正在仓库里堆放箱子。
3. 3. The books are stacked in the library.
   书被整齐地堆放在图书馆里。