Which of the following would be an example of the user of a product assuming the risk of harm?

a$.$ A man is injured by a power drill which has a faulty grip he was not aware of and was not apparent to him

b$.$ A restaurant owner who is scalded by boiling water when he uses a coffee machine which he has witnessed on several occasions malfunctioning and boiling water spilting out

c$.$ A woman who receives a severe electric shock when she accidentally touches a defective power source

d$.$ A gardener who fails to read the warning cautioning users of the proper way to operate a lawnmower, and is seriously injured