Doubt regarding Knowledge Check 12.2

iri36

Knowledge Check 12.2 asks which command will show the parent process IDs (PPIDs) for all the processes on the system. This question gives four possible options and marks only option 4 as the correct one:
1) ps aux
2) ps elf
3) ps-aux
4) ps -elf

I would like to know why multiple options are not possible if option 2 (ps elf) also shows the PPID of all the running processes. Why only option 4) is the correct answer?

Thanks

coop

ps -elf shows all processes on the system. ps elf (no dash) shows only those running under the current shell, terminal window

iri36

Ohh, that makes sense. Thank you!