Answer:
L
Explanation:
Most people prefer to use a unit of measurement that gives a number they can easily visualize, usually between 0.1 and 1000.
You wouldn't use centimetres, because that is a unit of length, and grams are a unit of mass.
The amount of milk in a half-gallon carton is about 2 L or 2000 mL, so you would measure the milk in litres (L).