The sun went down. The underlined word (down) is used here as a/an:

✅ কেন সঠিক: In ‘The sun went down’, ‘down’ modifies the verb ‘went’ and has no object, so it is an adverb.

❌ অন্য অপশন: If it had an object (e.g. ‘down the hill’), it would be a preposition.

💡 মনে রাখুন: Preposition needs an object; without an object the same word is usually an adverb.

📖 শব্দার্থ: অর্থ: সূর্য অস্ত গেল।