This actually depends on which level of education you are and what they are looking for. Most people though merely considers it a part of the Digestive System as the bile it stores is used during digestion.
I have seen however several people put it down as part of the bilary system or subsystem which responsible for the creation and distribution of bile.
Answer:
poop poop poop poopopopopopo
Explanation:
poi98uygtfrgtyuikolkijuhygtfrdef
This is true weight gain can effect a lot of things
