Which of the following is an example of a simile?

A simile is a figure of speech that directly compares two different things using the words "like" or "as" to highlight a particular quality or characteristic shared between them. The correct example, “He is as brave as a lion,” uses "as" to make a comparison between a person's bravery and that of a lion, effectively illustrating the idea that the person's courage is similar to the well-known bravery associated with lions.

This comparison enhances the imagery and allows readers to understand the degree of bravery being described. The other choices, while they contain figurative language, do not use "like" or "as" to make direct comparisons in the same manner as a simile does. For instance, saying, "She was a lion in battle" uses a metaphor rather than a simile, as it implies she embodies the characteristics of a lion without using "like" or "as."