Option 1: Resounding -> Similar to resonant; means loud, echoing, and reverberating.
Option 2: Cacophonous -> Harsh, discordant, jarring sounds; opposite quality to resonant's harmonious fullness.
Option 3: Smothered -> Muffled or suppressed sound, but doesn't directly oppose the quality of resonance.
Option 4: Pulsating -> Rhythmically vibrating; similar to resonant in conveying rhythmic sound waves.
Hence, Option 2: Cacophonous -> Resonant describes deep, full, harmonious sounds while cacophonous describes harsh, discordant, unpleasant sounds - they are opposite in terms of sound quality. -> correct