Which is the best example of a response to an external stimulus

Explanation:

2 Another example of external stimulus is temperature. When it is cold outside, your response is to get warm by putting on a jacket. If there is an external stimulus, there must also be an internal. An internal stimulus is a stimulus that comes from inside an organism.

well for one plants are always the producer, so a is the answer. a wolf is more of the consumer(predator) and the deer is the prey so i know those two are out of the question. also mushrooms are fungi/fungus so a is the producer.