"Why do sheep eat it?"
Translation:Proč jej žerou ovce?
Both the neuter demonstrative pronoun "to" and the neuter personal pronoun "ono" can function as the English "it". Those were the nominative forms. The accusative of "to" is also "to". The accusative of "ono" is "ho", "je", and "jej" (equivalent except for applicable sentence positions) without a preposition, and "ně" and "něj" (equivalent) after a preposition.
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Life would be too easy if that was true. It seems to be true only if the pronoun refers to the object of the sentence and it is a question. For sentences like "where is his house" the order would rather be "Kde je jeho dům?" But for "Where can I find him?" it is "Kde ho můžu najít?"
From Duolingo: Some of the forms can only appear in the second position in the clause (like the verb particle se). These "clitics" are the forms listed in italics [tě, ho]. Using these outside of the second position is an error, except when a higher priority second-place item, such as the verb particle, pushes the pronoun to the right. Using the two-syllable alternatives to the clitics in the second position tends to be emphatic, sometimes to the point of clashing with the ordering in the rest of the sentence, and thus also an error.