D.
My son is 5 1/2 and wants to shower alone. I use to wash my kids together (cuz it's easier), but I have a boy and a girl and he wants a shower now, not a bath. So I let him take a shower, but I put the soap on the scrubby and make sure he washes all his parts (I do his back) and I make sure to put shampoo in his hair and rub it in. I check him before I get him out for suds and then dry him off. But at 6 1/2 he's old enough.