The answer that most parents, (mostly moms) will give their child when they dont want them to do something or go somewhere. It is said because they know the child knows they have no answer, so they will simply say, Because i said so!
Billy: "Mom c'mon, please let me stay at Ben's tonight!"
Billy: "Dammit why not!"
Mother: "Because I said so!"
Billy: "That's not a answer mom!"
Mother: "I'll pick you up in a hour, bye" **click**