The word "fragrance" refers to a pleasant smell, which fits the context of the sentence where the flowers' smell is described as "enchanting."
- "Stench" means a strong and unpleasant smell, which doesn't fit the context of something enchanting.
- "Smell" is a general term for any kind of odor, but doesn't carry the same positive connotation.
- "Odour" is a neutral term that refers to any kind of smell, whether pleasant or unpleasant, so it doesn’t convey the same positive meaning as "fragrance."
Thus, the best choice is "fragrance."