Which one of the following is NOT a necessary assumption

Which one of the following is NOT a necessary assumption for the air-standard Otto cycle?

1. All processes are internally reversible.
2. Intake and exhaust processes are constant volume heat rejection processes.
3. The combustion process is a constant volume heat addition process.
4. The working fluid is an ideal gas with constant specific heats.

Intake process is the constant volume heat addition process
Hence (b) is not the right assumption