- A fish is a kind of scaled animal
- Protecting is a kind of function
- Scales are used for protection by scaled animals
- Therefore, the function of the scales of fish is to protect fish

Hence, the function of the scales of fish is to protect fish
[Question]What is the main function of scales on a fish?
[Context]- A fish is a kind of scaled animal 
- Protecting is a kind of function 
- Scales are used for protection by scaled animals