At the cellular level, leukoplakia typically shows a thickened keratin layer.

从细胞学层面看，口腔黏膜白斑的典型表现是增厚的角质层。

And elsewhere, striped deposits called rhythmites, show layers of sand and sediment laid down and flood after flood.

在其他地方，被称为韵律层理的条纹沉积物显示了一层又一层的沙子和沉积物，以及洪水泛滥。

But if I want to increase that level of formality, if I want to show an extra layer of politeness or be more indirect, then I can use either the progressive form or the past tense.

但如果我想增加正式程度，如果我想表现出额外的礼貌或更间接，那么我可以使用进行时或过去时。