Step 1: Recall which ores this method concentrates.
Froth flotation is the go-to method for concentrating sulphide ores.
Step 2: Focus on the wetting difference, not weight.
Sulphide ore particles have naturally hydrophobic surfaces, and collectors like pine oil coat them further, so oil sticks preferentially to the ore.
Step 3: Contrast with the gangue.
Gangue particles stay hydrophilic, remain wetted by water, and sink instead of rising with the froth.
Final answer: Option 3, ore particles are preferentially wetted by oil and gangue by water.