The line that exemplifies Lewis Carroll's use of opposites is:
“All this time the Guard was looking at her, first through a telescope, then through a microscope, and then through an opera-glass.”
This line illustrates the concept of opposites through the contrasting viewing instruments; a telescope is used for seeing distant objects (far away), while a microscope is used for viewing very small objects (close up). This juxtaposition emphasizes the difference between looking at something far away versus something very close, showcasing Carroll's playful use of opposites in language and perspective.