(1) She is a daughter of a policeman.
(2) She is the daughter of a policeman.
Does the (1) imply that her father policeman has more than one daughter?
Does the (2) imply that her father policeman has only one daughter?
How about this Example 2:
(1) This is a wheel of a truck.
(2) This is the wheel of a truck.
These two sentence doesn't quite give me the feeling that the truck has only one wheel.
So, why is that?
Is it because the number of children is something hard to predict while the number of wheels on a truck are usually more than one?