unable to select security options in disk utility

[anonymous4a]

I'm trying to delete my hard drive and restore my os x to factory settings.. When I go to disk utiity and select my main hard drive, I go to erase.. but security options is not clickable.. why is this ? I want to select zero out option in security options

 

[charlieegan3]

You can erase your main hard drive, it's where disk utility is stored.

 

[anonymous4a]

I forgot to mention, on startup, I held down cmd and R so I'm in recovery mode now. I clicked erase, but security option is unclickable