A water manometer is attached to a gas supply. A gas leak occurs, causing the pressure of the gas supply to decrease. What change occurs to the water level at $P$ and what change occurs to the water level at $Q$?
- Awater level at $P$ falls; water level at $Q$ falls
- Bwater level at $P$ falls; water level at $Q$ rises
- Cwater level at $P$ rises; water level at $Q$ falls
- Dwater level at $P$ rises; water level at $Q$ rises