D. "She dips a corner of her sleeve / like a brush into water"
A simile is a figure of speech that compares two things using the word "like" or "as." In this excerpt, the comparison "like a brush into water" directly compares the action of dipping the sleeve to the gentle motion of a brush being dipped into water. This creates a vivid image and is an example of a simile.
The other options do not use "like" or "as" to make a direct comparison, making them not similes: