OK, then, can anybody figure out from my screen shot what my problem is?
You are looking at System Root > All items. So you are looking at a certificate that does not belong to you, rather it belongs to the user System therefore you do not have the authority to delete or change them and the option down not appear in the context menu.
In the left hand pane of the Keychain Access window you see two certificate icons. If you select
My Certificates you will see the only the certificates owned by your user account and the context menu will have the items I listed. If you select
Certificates you will only see certificates owned by the system and their context menu is as shown in your screen shot.
