The answer is C: surroundings.
Explanation for each option:
A. Genes - While genes play a crucial role in determining the characteristics and behaviors of plants, the question specifically refers to how plants respond to external factors, not the genetic basis of these responses.
B. Light - Although light is one of the factors that plants respond to, the question encompasses a broader range of responses, including growth toward water and the sun, not just light.
C. Surroundings - This is the correct answer because the question describes how plants respond to various environmental stimuli, such as water, the sun, and light, which are all part of their surroundings.
D. Learned behaviors - Plants do not have learned behaviors in the way animals do, as their responses are innate and genetically programmed rather than learned through experience.
In summary, the correct answer is C: surroundings, as it encompasses the various environmental factors to which plants respond.