Questions & Answers about Tko vidi mladog radnika?
Why do we say mladog radnika instead of mlad radnik?
In this sentence, the worker is the object being seen. Because radnik (worker) is a masculine noun that is animate (a living person or animal), it takes the accusative ending -a to become radnika. Any adjective describing it must match, so mlad (young) takes the masculine animate accusative ending -og to become mladog.
Would the ending of mladog change if we were talking about an object instead of a person?
Yes! If you were saying "Who sees the young moon?" (moon is mjesec), the object is still masculine, but inanimate (not living). For inanimate masculine nouns in the accusative case, the noun and adjective just keep their normal dictionary forms. You would say Tko vidi mlad mjesec?
Why is Tko in its normal dictionary form here?
Tko means "who" and is the subject of the sentence—it's the unknown person doing the seeing. Because it is the subject, it stays in the nominative (default) case.
Why do we use the he/she form of the verb (vidi) with Tko?
In Croatian, the question word Tko (who) always takes the third-person singular form of the verb, just like "he" or "she" (on or ona). This works the same way in English: we say "Who sees?" (singular), not "Who see?".