Which of the following is an example of a plant responding to an external stimulus?

Science

Plants too are the living organisms of the ecosystem. They too respond to the external environmental stimuli. Phototropism is the best example for it. All of us know that for plants to grow light is necessary . Hence all plants  respond to the changes in the environment , and respond to it by growing their stems, roots, or leaves toward the direction of stimulus or away from the stimulus.

I think the answer for this question is  C.