The answer is E. Incense.
Odour, smell, and foul are all words that refer to the sense of smell. Fragrance is a pleasant smell. Incense is a substance that is burned to produce a pleasant smell.
Odour is a general term for a smell, whether it is pleasant or unpleasant. Smell is a more specific term that refers to the perception of a particular odour. Foul is an adjective that describes an odour that is unpleasant or disgusting. Fragrance is a noun that refers to a pleasant smell. Incense is a noun that refers to a substance that is burned to produce a pleasant smell.
Incense is different from the other words in the list because it is a substance that is burned, while the other words are all terms that refer to the sense of smell.