These days are ill-defined in my memory, running together and combining like a fresh watercolor painting left out in the rain what type of literary device is the author using here

Simile

Explanation:

In these lines, the author is employing a simile in order to provide a vivid image to the reader. The author tells us that his memories are "like a fresh watercolor painting left out in the rain." A simile is a comparison between two items that uses the words "like" or "as." This is one of the most common literary devices in English.

d is the best answer for this question.

the