Answer:The correct answer is -
avoiding the sun by looking for food at night.
Explanation:External stimulus can be described as any detectable signal/ change, which is present outside the body of living organism and enables the organism to respond towards it.
In the given options of this question, sun is an external stimulus that enables an organism to avoid it and search its food during night time.
Thus, avoiding sun and searching food during night time is the appropriate response towards the external stimulus, which is sun.
