A piece of wood is floating in water kept in a bottle. The bottle is connected to an air pump. Neglect the compressibility of water. When more air is pushed into the bottle from the pump, the piece of wood will float with (HC)

• Supplying air inside the bottle will increase the air pressure. 
• When the pressure of air inside the bottle increases it does not increase the weight of the wood nor density of the water. 
• So there will be no change in the submerged part.
• Any body submerged in water will balance its weight thanks to buoyant force, which is equal to the weight of the water displaced.
• If a piece of wood has a submerged height of h, then $\mathrm{B}={\mathrm{\rho }}_{\mathrm{w}}\mathrm{gh}=\mathrm{mg}$, where mg is the weight of the piece of wood.
• Because of this, the submerged height is independent of atmospheric pressure (pressure of air in bottle in this case). 
• Therefore, adding extra air to the bottle has no effect on the height of the submerged object.

Hence the correct answer is same part in the water.