A third-grade teacher is introducing figurative language. Which of the following sentences best demonstrates a simile?

This expression is an idiom, not a simile. It conveys heavy rain through a figurative phrase that does not involve a comparison using "like" or "as." While it creates a vivid image of rain, it does not fit the definition of a simile, which requires a direct comparison between two different entities.

This sentence employs alliteration and imagery but does not contain a simile. It describes the action of butterflies without comparing them to another object or concept. As there is no use of "like" or "as" for comparison, this sentence does not illustrate the figurative language characteristic of similes.

This phrase is a metaphor rather than a simile. It suggests that America combines various cultures and backgrounds into a cohesive society. Although it conveys a strong figurative meaning, it lacks the comparative structure typical of similes, as it does not use "like" or "as."