Inside a cylinder fitted with a tap is a fixed mass of gas $X$. A piston seals the gas and is free to slide either towards or away from the tap. After the tap is opened, the piston shifts a small distance to the right, in the direction of the tap. What can be deduced about the pressure of gas $X$?
- Abefore opening tap: less than atmospheric pressure; after opening tap: more than atmospheric pressure
- Bbefore opening tap: same as atmospheric pressure; after opening tap: more than atmospheric pressure
- Cbefore opening tap: more than atmospheric pressure; after opening tap: less than atmospheric pressure
- Dbefore opening tap: more than atmospheric pressure; after opening tap: same as atmospheric pressure