。
I smelled it.
Literal
I [topic-は] smell [object-を] sniffed.
匂い ('smell, odor, fragrance'). 嗅ぐ ('to smell, sniff') — specifically the active action of smelling (contrast with 匂いがする 'emit a smell'). 嗅ぐ uses a kanji not on the jouyou list, so often written in hiragana as かぐ.