This question tests the preposition that follows the adjective "worried" when expressing concern over something.
- Option A (To): "Worried to" is not a standard collocation in English.
- Option B (For): "Worried for" is occasionally used but suggests concern for someone's safety in a general sense, and it is not the most standard fit here.
- Option C (About): "Worried about" is the standard and natural collocation used to show concern about a specific matter, person, or condition, such as someone's health.
- Option D (Of): "Worried of" is grammatically incorrect in English.
The correct answer is C) About, so option 3 is the answer.