The device used in 'Light as wind on water laid' is

The device used in the phrase 'Light as wind on water laid' is a "simile." A simile is a figure of speech that compares two things using the words "like" or "as." In this phrase, the comparison is between the lightness of something and the way that wind feels when it moves over water. By using this simile, the author is able to convey the idea that the thing being described is very light and delicate, just as the wind is when it moves over water. Therefore, option B - "simile" - is the correct answer to this question.