Which of the following is an example of a simile?

The statement "Her smile was as bright as the sun" is a simile because it uses the word "as" to make a comparison between her smile and the brightness of the sun. Similes are literary devices that explicitly compare two different things, typically using “like” or “as,” to highlight a particular quality or characteristic. In this example, the comparison emphasizes the brightness of her smile, allowing readers to visualize it more vividly.

The other choices may contain comparisons or descriptive language, but they do not meet the criteria of a simile. For instance, while "He is the fastest sprinter in the world" presents a superlative statement, it doesn't employ a figurative comparison using "like" or "as." Similarly, "The wind howled like a wolf" employs the word "like" and is indeed a simile, but it is not the best example in contrast to the clarity and imagery provided by the smile comparison. Finally, "She runs faster than anyone else" uses a comparative form rather than an explicit figurative comparison.