In which sentence is the word ' past' used asa preposition?

• ক (খ) I called out to him as he ran past.
• খ Halima was a wonderful dancer, But she's past her prime. ✅ সঠিক উত্তর
• গ (ক) Writing letters is a thing of the past.
• ঘ (গ) I look back on the past without regret.