Hey there!
Even if there isn't anyone working on the circuit at the moment, it still may be exposed and activating it could cause a variety of problems. This means that whoever is present or whatever time you would activate the circuit is irrelevant as the switch should only be thrown after permission is given.
Logically, you would need permission from whoever ordered against throwing the switch in the first place, which should be the person who signed it. I believe that your answer will be "Operate this switch only after getting permission from the person who signed the tag", which is D.
Hope this helped you out! :-)