A process in which volume remains constant is called:
Isochoric process
Isothermal process
Adiabatic process
Isobaric process.
Isochoric Process
Here volume is kept constant. during each step of the process.
For example, the Heating of substance in a closed vessel (system) or non-expanding chamber.
The process is termed as isochoric in which volume remains constant throughout the change, i.e,
Hence, option number (1) is correct.