But the compiler is not recognizing the relationship name.Why is the inline query not able to recognize the relationship name.What may be possible problem?

I am doing the trailheads and I am stuck on one task. It asks me to create an object-specific action for the Event Object, but it always gives me an Error Message. When I go to Event>Button,Links & Actions> New Action, the Error Message: "Error: Create a relationship between this and another object to proceed." pops up. I tried numerous times to trouble shoot the problem and to create a look-up relationship but it doesnt let me creat any relationships for Events. 

Any Idea what I am doing wrong? I appreciate your help.