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Questions & Answers about O que lhes mostras?
Why is lhes before the verb instead of attached to the end with a hyphen?
Does lhes mean them or to them here?
It means to them. The verb mostrar (to show) gives something to someone, so it uses the indirect object pronoun lhes to represent the people being shown something.
How do we know the sentence is asking what you show, since the word tu is missing?