如果你在显微镜下观察这张纸，你就会看到纤维。
If you look at the paper under a microscope you will see the fibres.
当我们在显微镜下观察脏水时，我们会看到它们。
When we look at dirty water under the microscope, we shall see them.
一方面，有微小的微生物，只有在显微镜下才能看到它们。
On the one hand, there are tiny microbes and they can only be seen through a microscope.
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