- Food can be a source of an odor
- Smell is used for detecting odor
- So, smell can be used to detect food odors

- Sense is a kind of characteristic of an animal
- Smell is a kind of sense
- Hence, smell is a kind of characteristic of some animals

- Smell can be used to detect food odors
- Smell is a kind of characteristic of some animals
- Hence, smell is used for finding food by some animals

- Smell is used for finding food by some animals
- A fox is a kind of animal
- Hence, smell is used for finding food by foxes

Therefore, smell is used for finding food by foxes
Question
Which characteristic helps a fox find food?

Context
- Sense is a kind of characteristic of an animal 
- Smell is a kind of sense 
- Food can be a source of an odor 
- A fox is a kind of animal 
- Smell is used for detecting odor