well i tested it so i will explain it to you. you know that when you select 2 objects, one of them is surrounded by the color red and the other one is orange. the orange is the active one(the last one selected).when you do the parrent option the orange object will become the parrent and the red object will be the child. so the main thing you should know is when you do parrenting, the active object becomes the parrent.;)
